I was diagnosed with that myself and I'm currectly in an immobilizer from surgery i had almost a month ago. The crack you're feeling is youur arm slipping out of the socket. Your humerous arm bone connects into the glenoid socket and the buffer is called the labrun. Wrapped around that is your glenohumeral ligaments, the "noodle" ligaments that are loose. My surgery made those tighter.

Your shoulder is still loose so your arm is basically coming out of your socket because nothing is holding it in place. It is doing damage to your labrum at least and could be hurting your bones. I'd go back to see an orthopedic surgeon if you're still not better after five years. I had horrible side effects from mine not healing including winged and snapping scapula and myofascial pain syndrome because all me other muscles were trying to compensate.