The problem definitely occurs with entities -- I added code to make the player move more slowly when on top of an entity. I found this out using elevators. I kept "sinking into the floor", occasionally getting stuck inside an entity. Usually just thrown off the entity at high speed.

Level geometry is much more stable than entities. With level geometry the problem is more with moving at with higher velocity towards walls. Sometimes the moving entity gets stuck but other times it passes all the way through.

I still want to identify precisely what I think the issues are from my perspective. That way, I'll know if it's a bug or just a question of my learning to use the system appropriately. I appreciate your help very much, Marco.

I'll get to work on my "experiments" (putting on mad scientist costume as I type) and try to be as clear as possible about what I perceive as a problem.

Thanks again.