Yes.
About my fourth flight carrying jumpers in a C 185 (with really no jump pilot training whatever) I had the plane slowed back to about 55 MPH (it was STOL kitted). The JM loved it when I flew really slowly on jump run, and I liked to keep them happy.
Well, the three jumpers all climbed out, but did not jump. They went hand over hand up the wingstrut. Followed by the JM. I had four of them trailing the strut, and full rudder, and lots of aileron in to keep it straight with all of that unexpected drag. As I was about to yell out there "what the hell are you doing?". the JM yelled "Yahoo!", and they were gone. Well with all that control applied, as the plane reached the stall, then suddenly the drag was gone, the thing just tumbled, I had no idea which way was up. I was really concerned that I might hit a jumper, but had no idea where they were, and no control anyway. Some kind of spin/spiral dive/split S/immellman recovery worked, and all was fine.
After that, I insisted on briefings before jumpers exited.