I have a major problem regarding Itunes mismatching sort-artists to the actual artist and reverting edits i make

this has been ongoing for about one and a half years, it started when one day i signed in and discovered that nearly everly. single. song was mismatched all over the place, it took me a while to understand why because i'm not tech savvy, but discovered that the sorting on each song had changed (for example, a piece by Beethoven would have the artist as Beethoven, but the Sort Artist under David Bowie etc...) I spent a year redoing everything, going through every single artist manually and changing it, hoping that would be the end of it. But now it's happening again, I do a thing where I change the Sort Artist and the Viewed Artist of an album to a certain classical composer so that it's all under his name in one place, however every week or so when i sign into itunes, it's all reverted back to the original artist name (IN NAME ONLY) by that i mean when i click on the piece of music, it immediately resets and jumps back down to where it should be (Händel for example) this is extremely frustrating as each time i sync my ipod it gets the mismatched artist info again, how in ** name do i stop this?

for clarification: with the pieces on which i click to revert back to normal, when i check their info, they have not only the correct artist, but also the correct sorting artist in place which i have put there, so it makes no sense why they would revert