Getting abandoned is not a bug, even though it needs to be fixed since it happens too easily and makes this ability not very useful. It is warned in the description of the critical repair that crew are vulnerable while repairing, so repair it while not in combat. It's similar to the Sturmtiger's reload which crew becomes vulnerable while reloading and you should do it in safety.
There is a bug, which when you use the ability,
after the ability is finished and you are set to go, each penetrating shot will decrew your vehicle. That's what we are talking about. There was a video here but I could not find it.