As @supersalad expertly demonstrated, it could be either. Should be easy to find out which one though by working the levers manually, both should snap back instantly. Should be a fair bit of resistance on the body lever also.
I'd still guess at it being gunk on the aperture blades in the lens causing problems, with perhaps the MV body lever having a bit more snap on stop down.
As @supersalad expertly demonstrated, it could be either. Should be easy to find out which one though by working the levers manually, both should snap back instantly. Should be a fair bit of resistance on the body lever also.
I'd still guess at it being gunk on the aperture blades in the lens causing problems, with perhaps the MV body lever having a bit more snap on stop down.