Use the procedure on a representative sample, keep the evidence, and record the next action.
Find where the loss starts
- In Search Console compare equal periods; split by Web, country, device, query, and page. Do not compare unlike seasons.
- Check whether impressions fell first. If impressions are stable but clicks fall, inspect CTR and the current search result.
- Compare affected pages and queries with unaffected ones; note dates of releases, redirects, robots, and template changes.
- Write one evidence-backed cause to test, the affected URLs, owner, and review date. A correlation alone does not prove the cause.