I posted something about this a while ago but without a response.
I created a test in which a slider controlled the angle of a "floor" object. The "ball" that would drop would interact with the floor object when it was flat. Sometimes the ball would bounce as expected. Other times, the ball would pulsate vertically. Other times the ball would not bounce.
When I tilted the floor, the ball would sometimes hang at the bottom, ignoring the tilt, or it would move to a position and move rhythmically.
I never figured out the problem.
Here's the file:
Physics Test.hype.zip (29.4 KB)