Python Works in a Shell but Fails in Cron: Test the CWD
Reproduce FileNotFoundError by changing only the working directory, then separate paths, interpreter selection and permissions.
Checklists
Cloudflare 5xx: Trace 504 Errors from Edge to Origin
Compare an observed Nginx 504, Search Console notification time, and a later crawl. Use Cf-Ray and origin responses while keeping unproven causes separate.
Tailscale SSH Policy Denied: Node vs User Rules
Distinguish Tailscale SSH node-policy and user-policy denial. Check the matching SSH rule, OS user, port 22 access, and check-mode reauthentication.