I had same issue with my right shoulder.  Docs said it was partial tear and didn’t want surgery.  So I spent a lot of time on here addressing internal rotation and has improved the majority of my pain symptoms.  It has taken a long time and I am still not 100% but I don’t have much pain.  This was back in 2010.  Nagging injuries are the most frustrating because you never seem to get the answer or fix you want.  I’d start seeing if your a 1 or 0 on internal rotation and start there.