Please tell us: Which function did you use? Do you write to a local drive or something in the network?
What do the access rights look like? Are you the owner of those files? Do other programs access the file at the same time (e.g. a player, indexer)? Does this happen only to this file or also to others? Can old files be manipulated?
Convert filename to tag. It happens to more than 1000 files out of 1400, all hosted on a local SDD, I own the files, I have full RW rights on them. I repeated the same modifications on the same set of files several times, and it happens randomly. No other programs access these files as I work on a copy
Possible but far stretched: I would be very unlucky if these tools decide to scan my library every time I want to update the tags... several times a day.
It should show specifically the version of the tag found in the file. Probable hints for bad files would be either missing tags, no length or specifically in the "Tag" column a text with the word "bad".
IMHO, such programs only jump into action if they detect a change. Modification of the tag data would be such a change.
So, does it happen if you use smaller batches?
Does it stop at a particular file?
I mean: if it
then it looks like the root cause does not originate in MP3tag or in the files but in the environment which hinders the process to complete.
If you find a file that stops the modifications, it would be nice if you could share it with us.
In such "random" cases, I suggest to check it by yourself.
You could try a tool like Procmon to see IF and WHAT process access your files during your Mp3tag changes. You can find a detailed "howto" for procmon here on this external (not affiliated) website:
Please be sure to start with a filter like the path to your AIF files. Otherwise the number of entries will be overwhelming: