31 Zombie Tags, 6 Duplicate Conversions: 4 Years of Agency Handover Damage

The situation

A UK jewellery brand had worked with 3 different agencies over 4 years. Each agency had added their own tracking without properly removing the previous setup. ROAS had been declining for 8 consecutive months. Their current agency had audited the tracking setup twice and confirmed it was "working fine." The client hired me for an independent audit.

The problem

The GTM container was a 4-year accumulation of conflicting configurations. 31 tags were still marked active that served no current purpose — firing rules from 2021 campaigns, A/B tests that had ended, tracking for platforms they no longer used. More critically: 6 separate Google Ads conversion actions were all active and all counting the same purchase event as primary. Meta's pixel had been placed on the /cart page by the second agency and never corrected — meaning customers who abandoned cart were being tracked as purchasers, and actual purchase confirmations were completely invisible.

What we did

1. Full GTM container audit — catalogued all 43 active tags, traced each to its origin, confirmed its current firing behavior and whether it was still needed
2. Identified and removed all 31 legacy zombie tags, eliminating all firing conflicts and tag interference
3. Removed 5 of the 6 duplicate Google conversion actions — kept the cleanest implementation as the single primary purchase conversion
4. Rebuilt Meta tracking from scratch: pixel moved to the correct order confirmation page, CAPI added via Shopify webhook, full deduplication configured
5. Documented every change with before/after screenshots and a written handover document

Why it worked

Agency handovers without proper audits are one of the most common sources of tracking disaster. Each agency assumes the previous setup was correct and builds on top of it. Over time, the container becomes a graveyard of conflicting configurations that each appear "fine" in isolation but interact in ways that corrupt data at the platform level. A proper audit means reading every tag, not just running a surface-level diagnostic tool.