last 30 seconds of almost every song skips

I have a pretty large library, have been a itunes user for many many years. I believe I got my first ipod in 2001 or so. Anyway, I switched to android about 2 years ago because I was getting too annoyed with apple not being able to help. Well, I came back, it turns out android isn't much better. So now I reloaded my playlists from before and the ones from MusicBee. The old ones, the ones stored in my apple account, all have songs, most of the songs, skip the last 30 seconds or so. I deleted the songs from one of my playlists and re-added them to it. Same issue. I deleted it altogether and re-loaded the file. Now it works. My question is this, why did these files seem to get corrupted while stored on the account? Will I have to rebuild all my playlists (there are quite a few.) Will I need to remove all songs from my library and reload them. I hope not, it takes the better part of the day to do, and you cannot use itunes for anything while it is loading files.