Unless the game is literally unplayable, that's how it's supposed to be.
Removing Jeff and Slender's ability to go through walls during the Boss Rush would make them too easy.
I have a game on this website called "Dragons of Mysteria" that's still in development (and sorta struggling to get noticed more), and I ended up finding out that there are other games on this website also having "Mysteria" in their name.
So I thought about making some kind of community board or discussion for everyone who has a "Mysteria" game.