That’s not so surprising. I know from my windows only times that setting up from a clean install was the solution to everything (and it definitely is a good thing to do in many cases), but it is not a solution to everything. It just makes it very unlikely this is due to disk and thus database corruption. In my opinion you shouldn’t invest any more time in the “reinstall” vector - I just didn’t write that because without having an alternative idea, it just sounds like me being an a***ole.
That’s more interesting. If the reason isn’t that you just never looked closely enough before, this is a pointer that maybe something changed between the last time it worked and when you noticed it doesn’t - but I guess you have thought that over and over already.
That’s good, but that’s not enough. Probably - I don’t know the capabilities of these programs but I highly doubt they do anything than reading one specific metadata field. Digikam operates on various ones for compatibility with all kinds of programs and also for nested tag support, and if the wrong one is “corrupted”, that might through it off (it shouldn’t of course, but it did in the far past and might still now).