I haven't tested the save myself but my concern is that there may in fact exist literally impossible situations (that's what the op claims).
Difficulty, even in the extreme, is fine (especially on insane difficulty which this was) but absolute gamestoppers should be avoided imo. Or, I dunno, maybe he just should've brought more shields. Or maybe one should just accept non-winnable scenarios and retreat + airstrike? I just don't want an exploit fix to be a game breaking bug (not claiming it's necessarily the case here).