Was going to suggest this if no one else had. Most men are socialized to interact side by side or around an activity and not face-to-face, since face-to-face means head-to-head which is combative.

@nvoigt, OP mentioned "they all" which suggests more than two.

I dislike the idea of punishing everyone because of one bad actor. You can catch him two or three times and then tell him, and just him, that because of the issues he'll need to submit by email. Document it, of course, so if he complains you can say why he's being targeted.