Though it's not a complete fix, I have found a way to get rid of old saves.
I hope you have a similar file setup as me is all haha
Go to c:\users\(accountname)\appdata\Glitch Pitch\
and the idol manager folder will be there, it's not the install folder, but it's the folder where all the data is kept, so deleting it SHOULD basically make your game a clean slate... for me at least. I recommend backing up the folder to a different location before deleting it though, in case there's something different to your setup than mine dkglfd