Highlighted-only PDFs "corrupted" after update

After updating to iOS 17.4.1 on my 6th gen iPad All the highlighted PDFs it contained are now somehow corupted and won't open. It already happened and that time I thought it was a bug of some sort but apparently it's a proper issue since it happened again to all the PDFs I highlighted with such diligency.

What I find interesting is that If I try to move one of the "corrupted" pdf to another folder i get an error message saying that the file does not exist or has been moved to a folder that does not exists.

I do find such an error so evident that I don't understand why no one complained before about it.

I am using the default iOS app file viewer and file manager by the way, both to highlight and reach the files.

Does anyone know how to fix the problem?