Laggy collisions between 2 simple objects in Godot 4 3D

Hello all!

I am writing a small 3D game and am noticing a performance issue when running the game. When there is collision between my player character (capsule) and the plane, I get about 2FPS. However, when jumping and in the air, I get the normal 57-ish FPS. Does anyone know why this happens? How can I fix it?

My code is the same as the default code, except for line 17:

Nevermind, I solved it! Turns out I was using the single convex collision sibling on the mesh instead of the simplified one.