That'what I'm talkin'about! The G5 cover is doing something like what I was thinking...block the bolt from being able to completely un-thread!
Maybe some kind of disc or puck could be epoxied to the inside of the C5 cover as one potential way to stop the bolt, if it were still a problem?
I red loctite-ed mine a while back, but next time I'm in there I'll see what I can do...just in case all else fails!
Meanwhile, I think I'll google Nordlocks and see what I'm missing...