Physics objects intermittently bouncing using Chipmunk

I’m trying to develop a platformer using chipmunk physics, and everything behaves properly for some time, and then all of the dynamic bodies will simultaneously jump off of the ground (a static rectangle object). I’ve already set restitution to zero, and I’ve already tried changing presolve and postsolve velocity to zero with no effect.

Also, when I drag the debug window and let go, the dynamic bodies will jump off the ground.

I’m using cocoStudio with 3.6 and Visual Studio.

Never mind, I fixed it by manually stepping the physics.