Thank you for this thread! Something is clearly amiss with iTunes 12.9.4,102. I'm using a previous version of iTunes on another computer (also Windows 10) with the same music files and they all work fine.
In my iTunes library, each song is identified under the 'Kind' field as a WAV, MPEG, Purchased AAC, or AAC audio file. Using the 12.9.4.102 version, the WAV, MPEG, and Purchased AAC files all work fine. The ones that don't work are the AAC audio files that were edited using my wave editing software (WavePad Sound Editor by NCH Software). When attempted to play now, the duration is changed to 789:57:13 and it does not play.
I can remove the hundreds of music files affected from my iTunes library, then save them in another format and add back to my library, but that would be a huge undertaking. Not only would I lose all the data including number of plays, date added, etc., but also many of the songs are included in multiple playlists, so I would have to manually go through each playlist and reinsert each of the reformatted songs one by one. Not feasible!
I did uninstall this newer version, and uploaded a previous version, but I could then not access my library. I was getting the message that my iTunes Library.itl file was from a newer version (i.e., 12.9.4.102) and this did not work with a previous version. Until Apple can fix this issue, it seems this is the most feasible path to go, but when downgrading to a previous version, how can you restore a compatible Library.itl file so the songs will play?
It seems Apple is unwilling to, but can someone here summarize the step by step procedure for going back to a previous version? I'm using Windows 10. Thank you!