Does MP3Tag have any restrictions on filename and/or path length? I just noticed tonight, while attempting to modify some tags in FLAC and MP3 files that I had already custom-tagged last week, that MP3Tag reported that it was unable to access certain files for writing, although those files were successfully loaded into MP3Tag and existing tags read and displayed. The files it had problems writing to all have long filenames, and all of those filenames had been generated by me via MP3Tag from track numbers and titles. The longest filename of the problem files was 68 characters, including ".flac", and the full path with filename was 273 characters. I made a copy of the file with only 43 characters in the filename (248 characters path + name), and MP3Tag had no trouble writing modified tags to it.
I also noticed that my file manager of choice (Directory Opus v11.19) would not display track length or descriptions in its lister window for all the long-filename files, but still correctly displayed the contents of the COMMENT tags for them. It looks like the longest path + name I can have in order for Directory Opus to report track length and descriptions is 259 characters.
I don't remember ever coming across this problem before with either MP3Tag or Directory Opus, so I wonder if this is something that has maybe been caused by a recent change to my system?
By the way, all of these files play without problems in various media players (foobar2000, PotPlayer), and have their media details correctly reported by MediaInfo.