Wow.... I somehow, at first, suspected it was dangerous code, which is why I submitted it here. However, it's not.

It's not an error like that because the bullet would stop at the wall. This leaves passable and push. It's not passable, because the player still collides with the wall.

It's push:

When I made a shotgun code, I gave each of the bullets a push number, which if you made over 1 bullet this push went down for each.(so they couldn't collide with each other). I watched the variable that controlled push, and indeed after the first time its push became 1. I stopped this, and everything is fine now.

Just goes to show, that a bit of logical thinking can do wonders... Thanks for the contributions anyway, and I'll consider dangerous instructions more carefully in the future too.