I forget the bosses name, but he is the one (bomber) in the barn with the rangers/shooters up on platforms along 2 walls of the barn. When I run up to those platforms on 2 flights of stairs and we finish the first 2 shooters and walk/run over to take care of the long wall of shooters, there is a line that I can cross back and forth in which all the shooters on that long platform disappear and re-appear from my player’s perspective.
It seems there are some graphics glitches in which objects are obstructed inappropriately. I’ve seen this happen in some jumping puzzles as well.