Fix Meta Purchase Event Inflation (GTM + Stape + Shopify) – NO REBUILD

Fix Meta Purchase Event Inflation (GTM + Stape + Shopify) – NO REBUILD

Description:
I need an experienced tracking specialist to FIX (not rebuild) my current setup:

Shopify → DataLayer → GTM Web → GTM Server (Stape) → Meta CAPI

Current issue:

Meta is over-reporting purchases compared to Shopify
Likely duplicate firing or deduplication issue

IMPORTANT (DO NOT IGNORE):

Do NOT change Pixel ID
Do NOT rename Purchase event
Do NOT rebuild tracking
Do NOT disconnect current setup
Must preserve Meta learning phase

Scope:

Identify source of duplicate/inflated purchase events
Fix event_id deduplication between browser + server
Ensure only ONE purchase is counted per order
Improve match quality (if needed)
Check timing delays (optional if relevant)

Requirements:

Proven experience with:
GTM (Web + Server containers)
Stape.io
Meta Conversion API
Event deduplication (event_id)

Timeline: 2–3 days