Collision Bug

I've got a weird collision bug with missiles that I can launch. When my missiles hit a mesh plane with a low enough angle, they just stop and the collision is not detected in the OnCollision function. Sometimes they even stop and then "rebound" to get stuck farther. The missiles are almost parallel to the ground when it happens. I've put a fail-safe that detects if the missile is stuck and translate it 0,1 lower to force the collision, put I'd like to know how to really fix that bug.

It may not be related, but the collision detection is set to continuous so it never simply go through the plane. My missiles are Rigidbodies and travel with a force, not a manually set velocity. Gravity is on too.

Thanks.