could you explain a little more?
On your way up you can't reach LO? and at what point does it start to fail?
I have a blown out shoulder that took me 2 years to recover and I had a similar problem with my ROM but mine was on the way down. Once I reached where my arms were parallel I had about one more inch I could go down. If I went any lower, I didn't have pain by my ligaments were damaged to the point where my right arm was basically locked at that position. I couldn't go up or down, but like I said no pain, just locked up.
If you are having something similar but on the opposite I would do a couple heavy lifts followed by a low weight high rep set that allowed me a full ROM and after time of doing that I was able to get to the point I mentioned above where just after level I have to stop, but prior to that it was much higher in my ROM that it would lock up