After updating Lightroom Classic to v14 and converted my database, all the edited photos that had a "Subject Mask" applied now have an empty mask with a warning and exclamation mark (!).
If I let Lightroom correct the mask pushing the exclamation mark on a single photo, it seems the correct subject is selected, keeping the edits. If I do the same with multiple photos together it appears teh usual form that tells that the AI masks are recalculated, but at the end all the masks are still empty with warnings.