When an already-fixed bug still reproduces, check the deployed image date first
A bug that had merged fixes kept reproducing in production; root cause was the deploy, not the code.
Merging to main does not change what production runs. A bug whose fix is verified-green-and-merged can still reproduce because the running container image predates the fix. docker inspect <name> --format {{.Created}} revealing an image built weeks before the merge is the instant tell — it short-circuits a whole re-debug of code that is already correct. Same applies to settings caches: a process that reads config once at boot will not pick up a file edit until it restarts, so activate-a-flag steps need an explicit restart, not just the file write.
Before re-debugging a symptom whose fix is supposedly shipped, compare the deployed artifact build time against the merge time of the fix; only debug code once you confirm that code is actually running.