Andrew Yim
7c5efea817
Renumber 12 existing skills to new ranges: - SEO: 11→13, 12→18, 13→16, 14→17, 15→14, 16→15, 17→29, 18→30, 19→12 - GTM: 20→60, 21→61, 22→62 Update cross-references in gateway architect/builder skills, GTM guardian README, CLAUDE.md (skill tables + directory layout), and AGENTS.md (domain routing ranges). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
212 lines
4.8 KiB
Markdown
212 lines
4.8 KiB
Markdown
# Common GTM Issues & Fixes
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## Container Issues
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### GTM Not Firing
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**Symptoms**: No GTM requests in network tab
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**Causes**:
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1. Script blocked by ad blocker
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2. Script placed after closing body tag
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3. JavaScript error before GTM loads
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4. Consent management blocking GTM
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**Fix**:
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```html
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<!-- Place immediately after opening <head> tag -->
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<script>(function(w,d,s,l,i){...})(window,document,'script','dataLayer','GTM-XXXXXX');</script>
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```
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### Multiple Containers Conflict
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**Symptoms**: Duplicate events, inconsistent data
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**Causes**:
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1. Legacy container not removed
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2. Different teams installed separate containers
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3. Theme/plugin auto-installed GTM
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**Fix**:
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1. Audit all containers in source
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2. Consolidate to single container
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3. Use GTM environments for staging/prod
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### Container ID Mismatch
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**Symptoms**: Tags not firing, wrong property receiving data
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**Causes**:
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1. Dev/staging container on production
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2. Copy-paste error during installation
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**Fix**: Verify container ID matches GTM account
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---
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## DataLayer Issues
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### DataLayer Not Initialized
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**Symptoms**: First push events lost
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**Code Error**:
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```javascript
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// Wrong - GTM loads before dataLayer exists
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<script>GTM snippet</script>
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dataLayer.push({...});
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```
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**Fix**:
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```javascript
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// Correct - Initialize dataLayer first
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<script>window.dataLayer = window.dataLayer || [];</script>
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<script>GTM snippet</script>
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```
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### Case Sensitivity Issues
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**Symptoms**: Triggers not matching
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**Example**:
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```javascript
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// DataLayer pushes "AddToCart"
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dataLayer.push({ event: "AddToCart" });
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// But GTM trigger looks for "addToCart" - won't match!
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```
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**Fix**: Standardize event naming (recommend lowercase with underscores)
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### Wrong Data Types
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**Symptoms**: Calculations wrong in GA4, missing data
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**Example**:
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```javascript
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// Wrong - price as string
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dataLayer.push({ ecommerce: { value: "29.99" }});
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// Correct - price as number
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dataLayer.push({ ecommerce: { value: 29.99 }});
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```
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### Timing Issues
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**Symptoms**: Events fire before data available
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**Cause**: DataLayer push happens after tag fires
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**Fix**: Use "Custom Event" trigger instead of "Page View"
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---
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## Tag Issues
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### Tag Not Firing
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**Checklist**:
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1. ✓ Trigger conditions met?
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2. ✓ Trigger enabled?
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3. ✓ Tag not paused?
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4. ✓ No blocking triggers active?
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5. ✓ Consent mode not blocking?
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**Debug Steps**:
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1. GTM Preview > Check Tags Fired
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2. Verify trigger shows green check
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3. Check Variables tab for expected values
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### Duplicate Tag Firing
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**Symptoms**: Events counted 2x in GA4
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**Causes**:
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1. Multiple triggers on same action
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2. Page re-renders triggering again
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3. SPA virtual pageviews firing multiple times
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**Fix**:
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1. Add "Once per event" tag firing option
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2. Use trigger groups to control firing
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3. Add conditions to prevent re-firing
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### Wrong Parameters Sent
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**Symptoms**: Data appears in wrong fields in GA4
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**Debug**:
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1. GTM Preview > Tags > Show fired tag
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2. Check "Values" sent with tag
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3. Compare with expected parameters
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---
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## E-commerce Issues
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### Missing Transaction ID
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**Symptoms**: Duplicate purchases counted
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**Fix**: Ensure unique `transaction_id` generated server-side
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### Items Array Empty
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**Symptoms**: Revenue tracked but no products
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**Check**: `ecommerce.items` array populated
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### Value Mismatch
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**Symptoms**: Revenue doesn't match actual
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**Causes**:
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1. Tax/shipping included inconsistently
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2. Currency conversion issues
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3. Discount applied incorrectly
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### Purchase Event Fires Multiple Times
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**Symptoms**: Same order tracked 2-3x
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**Causes**:
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1. Page refresh on confirmation
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2. Browser back button
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3. Email link revisit
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**Fix**:
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```javascript
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// Check if already tracked
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if (!sessionStorage.getItem('purchase_' + transaction_id)) {
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dataLayer.push({ event: 'purchase', ... });
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sessionStorage.setItem('purchase_' + transaction_id, 'true');
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}
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```
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---
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## Consent Mode Issues
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### Tags Blocked by Consent
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**Symptoms**: Tags show "Blocked by consent" in Preview
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**Fix**:
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1. Verify consent mode implementation
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2. Check default consent state
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3. Test with consent granted
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### Consent Not Updating
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**Symptoms**: Tags stay blocked after user accepts
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**Fix**: Verify `gtag('consent', 'update', {...})` fires on accept
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---
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## SPA (Single Page App) Issues
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### Pageviews Not Tracking Navigation
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**Symptoms**: Only initial pageview tracked
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**Cause**: No page reload on route change
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**Fix**: Implement History Change trigger or custom event:
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```javascript
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// On route change
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dataLayer.push({
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event: 'virtual_pageview',
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page_path: newPath,
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page_title: newTitle
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});
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```
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### Events Fire on Old Page Data
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**Symptoms**: Wrong page_path in events
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**Fix**: Update page variables before event push
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---
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## Performance Issues
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### Tags Slowing Page Load
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**Symptoms**: High LCP, slow TTI
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**Causes**:
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1. Too many synchronous tags
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2. Large third-party scripts
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3. Tags in wrong firing sequence
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**Fix**:
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1. Use tag sequencing
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2. Load non-critical tags on Window Loaded
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3. Defer marketing tags
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