The new MARC overlay rules can prevent edits to certain MARC fields. We don't give any indication when that's happening. To recreate: - set a rule on marc-overlay-rules.pl for module=source, filter=Staff client MARC editor, tag=020, preset=protect - find a record with an 020 - edit the record, delete the 020, save. confirm the interface allows all of this - confirm the 020 is still there, but no indication of why Something here should inform the user of what's going on. Highlighting of the tag within the edit interface? A popup on saving?
I wrote a patch on https://bugs.koha-community.org/bugzilla3/attachment.cgi?id=126667 Can be useful to start.