Physics Woes : Objects push me and make me fly!

I’m making a puzzle adventure game, and as such I’m using physical objects a lot. Now when I was prototyping games in UDK, I never had this problem. I made them have physics, so I could move, stack or use things to cross a ravine, or stack objects so I could climb out of some situation.

Now in UE4, my physical objects make me jitter and bounce at best when I climb on them, and at worst they propel the object I’m on and me. My son who frequently tests my game for me, has discovered if he grabs the object and holds it, while climbing onto it, he can start flying like he’s surfing. He has a lot of control actually which is impressive, except that it’s not what I want (although I make a mental note to maybe revisit this as a game).

Does anyone have any ideas why my objects may be propelling me?