Using your assets, I was still unable to reproduce the jittering effect. However, you might be seeing the issue because of the collision.
How are you creating the collision for the ramp and wall? I didn’t see where the .fbx files included any custom collision. So for testing I generated some inside the editor and also tried ‘Use Complex as Simple’ (which we don’t recommend because it can become taxing and doesn’t have the best collision/physics performance). Both worked fine on my end.
Maybe try using custom collision and see if the jittering goes away?
If not, feel free to upload the test project you mentioned.