This is still consistently an issue. E.g. after deploying https://gerrit.wikimedia.org/r/666245, the server keeps producing fresh HTTP responses from Apache with old PHP code. Same as last time, it does not appear to be correcting itself, it just stays there presumably until a root does a hard Apache or php-fpm restart.
Maybe it has something to do with the symlinks used by /srv/deployment? Or maybe opcache is configured on this host to cache forever and never look at file paths?
Tagging SRE and RelEng. I don't know who the first respondent is for this service. It seems that since Dec 2020 (ref T149924) it is basically become impossible to deploy changes to integration.wm.o and doc.wm.o. The only way changes become applies is if a root SRE restarts Apache and/or php-fpm locally on the doc1001 backend.