Backups had not been tested for a while and turned out to be unusable. When I launch import-db it almost immediately fails with "import failed" without any more details.
So unfortunately no - I have no working backups from before this issue started
Besides - turns out that it started at least 3 weeks ago. Probably even more. I'd really like to not lose all those changes made during this time because of one bad entry.
There are some scripts around here that can supposedly decode object data. I'll try those and see if I can spot the damaged object.