The platform (Kinematic Rigidbody) is moved using the Animator, which teleports the transform each frame. When you teleport two colliders using transform modifications on top of each other like this, there may be violent depenetration or other undefined behaviours when PhysX tries to separate them. The correct course of action would be to use Rigidbody.MovePosition for the platform, which takes into account the collisions and should be much more stable.
Alternatively, one can utilize "Animation.animatePhysics" if using legacy animations or "Animator.updateMode" set to "AnimatePhysics" to greatly reduce, if not circumvent the issue entirely and still use the Animator to move a kinematic RigidBody.
Also helps to decrease the depenetration velocity for the bodies, or increasing the solver iteration count in Physics Project Settings