I see. My game involves drawing objects with the mouse and then turning those into physics objects, so it is normal for each collision polygon to have high double-digit or even more than 100 vertices in them. Maybe that's why. I also enabled collision detection to play a sound effect, but I made it so that it disabled itself after one collision, so I don't think that's the main problem. All my physics code is in _physics_process as you said though.