I know exactly what you mean. I was doing pretty well with PT until I started using weights. At first I had problems doing tricep strengthening with a whopping 2lb weight. I think I may have been gripping the weight to tight or something. I tried again and focused on not gripping so tight I have been doing ok with it ever since with that exercise. But, recently I started doing some internal/external rotation with weights that flared my shoulder blade pain up to were it was before therapy started. I'm probably going to only do half the reps and see if I can tolerate that. Hoping that with time it will get easier. Which exercises flare you up?