Did you put the plastic screw cover inside the outdrive like the ones in the diff opposite the diff nut? If you leave that out it will pop out. I highly suggest following the manual and mot adding additional foam. Because of the angle of the front center outdrive if its pushed in to far it could cause too much bind.
I drove the car last night for the first time and my first impressions of the car are positive. It was lazy getting in and out but a few small tweaks and she came alive. Didnt have any issues with the center driveline popping out and I run a 6.5 with 20% esc timing.
I did miss that and have put it in. Thanks for the catch.