I'm extremely flexible and don't feel pain well.
Add 6 years of BJJ and no surprise that things go wrong.
The shoulders started to act up ~5 years ago and I've gone to various doctors every couple of years. Basically there was a "burny feeling" that I guess is what other people call "pain",I didn't know what it was, iced it, and kept on training BJJ. Now I know to stop whatever I'm doing when I feel that feeling.
Also, usually when I go see a doctor they insist I'm fine and give me NSAIDs. I don't...present pain well(obviously) and they think I'm there for drugs or a am a hypochondriac, give me exercise bands and tell me to do the mobility exercises, which I do.
What I have been doing wrong is not insisting on MRI, but I have usually have full mobility and no pain in most of real life.
Deadlifting seems to have cured my upper back/back of shoulders pain, but now the front is acting up.