Shadow Glitches on CC Objects

So I recently downloaded some really cute cc objects and noticed a few of them are broken. These items are really hard to find though so I don’t want to just throw them out, I was hoping someone could tell me how to fix them. I’d ask the cc creator themselves but they have left the community and are no longer updating their cc.

I’m not planning on redistributing the fixed items, I just want to be able to use them in my game.

These are the objects and they all seem to have the same problem, no matter where I place them or what lighting they still look like this. (the pink chairs on the right also shapeshift at certain distances but for now I just want to fix the shadows)

Any advice would be appreciated!