Can't assign two guides

Some activities need the option to have two (or more) guides or two instructors on the same activity. When I try to do this I get the following error message:

“Crew expectations staff role key has already been taken”

Example Case:

Morning two-tank boat dive with >10 divers requires a captain and two guides. Our preference is to have guides who are not only divemasters and not also instructors on the boat. Currently, it seems we cannot assign more than 1 staff member per role type.