I'd need the save just before you bailed your crew, or just as you loaded the gun crew. And passwords for both sides.
However - it's highly unlikely that the arty would fall in exactly the right place and make the German gun crew abandon, even after several goes (and/or whatever makes the swap happen is flaky as well so even if they do, then they don't
!) - so likely to be an utter pain to debug, if it even could happen.
I've never seen anything like that happen, or reports of it, so it would be useful to have the save to see if something can be seen from it.
If all you have is a save where the swap has already occurred, then that would not be any use at all.
Cheers
Andy