I tried playing the Backer Build, despite the stuttering problems, and I got in strange situations with my Heavy: first, I was inside an hangar and I decided to blow up the wall onthe opposite side of the building to kill a crabman on the other side of the wall. For some reason after the shot the heavy couldn’t move: only his square was highlighted in orage and no movement was possible. The next turn it was the same. At the third turn I decided to investigate the issue and I noticd that his feet were trapped inside some debris that probably fell on him after launching the rocket. Luckly I managed to free him by free-aiming the debris at his feet. I don’t think this feature was thought as a possible save to these situation, but it worked.
And it happened again: the heavy was on the top of the same hangar, shooting the Crab Queen, and a crabman launched a granade on the roof, which collapsed and left the heavy mostly unharmed but with his feet stuck again in some debris (this time another granade freed him of his concrete chains).
Off Topic: Heavy is super useful against the QUeen! At least, the machine gun is, since she’s so massive you can land every shot at mid range. And the assault can use the machine gun, I tested it.