The studio that I take lessons at actually calls this move "the dislocator" for exactly that reason. My instructor is constantly reminding me to warm up before practicing this move. I definitely haven’t mastered it yet, but someone advised me to start with both hands on the pole first (from a sit-n-spin position) and then try to let go with the outside arm and bring it around behind you. Does that make any sense?
Good luck! I hope your shoulder feels better!