Rarely see double crew credits so I think once is enough there.
But, if an actor does more than one role in a film and is credited for separate roles separately, then they will have multiple credits for that film.

I always pass on a crew member showing up the second time, but know I've seen a profile or 3 with double production credits. I think those are errors and others are right to keep it at 1 credit.
Sound people don't count, as they will often do 2-3 jobs on a film and do get credited for all creditable roles performed.