As Michal Kula noted on Mattermost, trying to log into http://localhost:8081/cgi-bin/koha/cataloguing/addbiblio.pl?biblionumber=9908 in main will yield a bizarre HTTP response that includes headers for a 403 response and a 200 response... This is partially due to bug 37040, but it's mostly due to a bug in addbiblio.pl where the form builder is generating a 403 that gets printed before the 200 response somehow...
If I capture STDOUT around a subsection of build_tabs(), I get 10 of these messages in STDOUT: [2024/06/06 01:12:47] [WARN] Status: 403 Forbidden Content-Type: text/plain; charset=ISO-8859-1 Status: 403 Forbidden Content-Type: text/plain; charset=ISO-8859-1 -- I suspect is has something to do with these warnings: [2024/06/06 00:08:33] [WARN] ERROR: Plugin marc21_orgcode.pl: ARRAY(0x561ffb8bfa98) at /kohadevbox/koha/Koha/UI/Form/Builder/Biblio.pm line 222. [2024/06/06 00:08:33] [WARN] ERROR: Plugin marc21_field_005.pl: ARRAY(0x561ffb8cdb60) at /kohadevbox/koha/Koha/UI/Form/Builder/Biblio.pm line 222.
Looks like a regression caused by bug 24879 Note that I'm not planning on working on this one.