I worked around this problem by removing the chocks prior to removing the ground equipment as part of pushback prep, and releasing the brakes normally when GSX calls to release them. The remove-brakes-then-chocks solution didn't work. I think something triggers something when the chocks and brakes are both engaged but the airplane is in the air. IniBuilds should look into this -- the "rolling" sounds play when the nose is raised but the airplane has a GS of 0 and is still parked, which supports my theory perfectly -- for some reason the plane thinks it is taxiing when in fact it is not.

Edited April 28Apr 28 by David Grundstrom

9 hours ago, David Grundstrom said:

I don't have pushback raise enabled, and it was a towbarless tug.

A Towbarless tug is supposed to raise the aircraft for push back, thats how they work.

It still raised the plane, so I'm not really sure what the "pushback raise" does when not enabled. But I turned it off because it was picking the nose up so high that sometimes the plane flopped on its tail and was not recoverable.