Pokemon Platinum Eternally Corrupted Save

[Waffle]

I've had this problem for years now, and I want to see if it's possible to fix. Everytime I boot up my game, a message shows up that says my save data is corrupted and the previous file will be loaded, and then the previous file is loaded, which means there's not really a problem if I save twice in a row, it's just annoying, but it does stop me from playing the post-game, which sucks. I'm pretty sure the reason this happens is because whoever had the copy previously must have messed around way too much with an action replay, but I have no idea how to fix it. Also, that broken file is the one that shows up if I try to edit the save using PKHeX, not my current file.

Here's my save file:

POKEMON PL.sav