5xx server errors
If Googlebot sees 5xx responses, it slows crawl rate within hours and may drop pages from the index within days. Check your server logs for the User-Agent 'Googlebot' and fix any timeouts, memory exhaustion, or rate-limit responses sent to crawlers.
Soft 404s
A page returns HTTP 200 but says 'No results' or has thin content. Google treats it as a 404 and drops it. Either add real content, return a true 404, or 301 to a relevant page.
Redirect chains and loops
Each hop costs crawl budget. Replace A→B→C with A→C. Loops (A→B→A) are catastrophic — Google abandons the URL.
Blocked by robots.txt that shouldn't be
Inspect each 'Blocked' URL in Search Console. Common culprits: Disallow: /*.js$ blocking critical CSS, or a wildcard left over from a staging environment.