Player sticks to bottom of platform

I have a player object with a dynamic rigidbody. I also have a moving platform with a box collider. The platform moves up and down, and other variations of the platform move left and right. My problem is that for whatever reason (and this doesn't happen with any of my other game objects), the player can jump upwards into the bottom side of the platform and just "stick" there. He basically dangles by his head underneath the platform and moves upward and downward with it. I have tried giving the platform a rigidbody as well as adding a platform effector to - neither helps. I have removed all script code relating to interaction with the platform and it still happens so it isn't a code bug. I'm really at a loss on this. My only thought is that the player jumping upward into a downward moving platform may somehow stick inside of the platform's collider, but that doesn't really make sense to me.