Severe Shoulder Pain

I have suffered shoulder sublaxications in the past playing rugby and played on, or if the pain has been really bad maybe took a week off and then came back when it has eased off.

Well a while ago it popped out when I was incline dumbell bench pressing, since then I have focused a lot on back exercises and chest exercises have became non existent and shoulder exercises have been chosen very carefully.

Today I was planning on training legs and shoulders, after performing all my mobilty work for my lower body I was planning on performing upper body mobility work… as I went to perform lying scapular floor slides my right shoulder was suddenly causing me pain in aorund the back of the shoulder.

Any ideas what this is please?