Have physics constraints changed in 4.8?

I have a blueprint that consists of a cube (physics turned on) with a physics constraint. I plan to manipulate this constraint with character actions, but until I press that action button, I want to have all linear and angular motions set to “Locked”.

The problem is, even with everything locked, when my character walks and collides with the cube it jostles in place before returning to it’s constrained orientation.

It seems that linear constraints work perfectly, while the rotational ones have wiggle to them.

This same set-up seems to work fine in 4.7 which leads me to believe that there’s something different happening in 4.8 that prevents me from having 100% constrained rotation. Is there something different in the code or am I just doing something wrong?