I see the same thing (with Havok and Ammo) and haven’t been able to find a nice way to solve this yet 
I believe this is because applying a linear velocity horizontally into a ramp causes the player (capsule) to slightly “clip through” or “tunnel through” the ramp. And when the player stops moving, the physics engine “pushes” the player out of the ramp. A potential way to solve this is to apply a linear velocity to the player at the same angle as the ramp.
@qq2315137135 's demo has some of the best ramp movement I’ve seen: Making one body push another using physics - #3 by qq2315137135