Are you using a dead hang?
I mean, if you're just hanging there without using your back to support you, I'd guess that you're putting more stress on your joints than you need to.
Kind of like keeping a slight bend in the knees when doing any standing movements, only backwards (if that makes sense).
Maybe try using your lats a little bit just to keep the strain off of your joints.
Or maybe you have shoulder weakness or imbalance issues. Are you doing alright with chin-ups or pull-ups?