Symptom
The distortion lives in the single-system tag manager view — it confirms tags executed but has no mechanism to verify whether each firing corresponded to a real user completing a real conversion action.
Cause
Client-side analytics tags fire on browser events that can be triggered by page reloads and SPA routing without corresponding server-side transactions — duplicate firing session stitching errors and bot leakage inflate the analytics count.
Impact
Budget decisions are made against CPA figures anchored to a conversion denominator 27% larger than the verified transaction population — the channel with the most inflated data appears the most efficient and receives the most budget.