@coco8 The symptoms you describe are common to my own issues. I don't have slipping rib syndrome, but I do have thoracic outlet syndrome and muscle tightness that extends from my jaw and neck through my chest and rib cage to my pelvis and it is tighter on one side. It pulls one hip bone forward which puts pressure on my lower back and causes sciatic pain. I have had ribs twist because of the tightness. I've had a frozen shoulder too. Sometimes exercise to strengthen muscles makes this kind of problem worse because the fascia holds the tightness and strength training makes it tighter. What helps me is myofascial release, so if you find a physical therapist who also does that, it might be worth exploring MFR to see if it helps you. A TOS diagnosis is often missed because it is only covered for a day in many medical schools, so finding a doctor who understand it is difficult. Look at medical centers who list TOS as a condition that they treat to find specialists. I have had pops and clicks in my spine because of the tightness and after a PT session, at one time I laid on and rolled on a wooden roller (Body back Roller) and it reset every level of my vertebrae with a click and I felt much better after it realigned itself. That was possible because my therapist had already manually loosened everything, so it went back in place willingly on its own. I can also stretch by twisting my spine which lets me know if I am maintaining proper movement. You may not need to manage pain if you can find a therapist who can get the fascia gliding again. Clearly you are stuck if all you have to do is arch your back and it pops. Maintaining proper posture is important to spinal discs too because if they are held with uneven pressure, it causes misalignment issues that can lead to bone spurs and disc problems from uneven pressure on the end plates of the vertebral discs. I know a lot about that through personal experience as a spine surgery patient. The bottom line is that when you can get everything properly aligned in your body from the head to the pelvis and properly moving again, it eases the pain. Misalignment leads to squishing nerves and sometimes blood vessels. If I can answer any more questions, please ask. It is kind of tough to recover when you have doctors looking at small parts of the problem and not seeing the entire problem as it relates to itself. Here are some links that further explain (you may want to show these to your specialists):
https://mskneurology.com/how-truly-treat-thoracic-outlet-syndrome/
https://www.mayoclinic.org/diseases-conditions/thoracic-outlet-syndrome/symptoms-causes/syc-20353988
https://mskneurology.com/identify-treat-lumbar-plexus-compression-syndrome-lpcs/
https://connect.mayoclinic.org/discussion/myofascial-release-therapy-mfr-for-treating-compression-and-pain/?pg=1#chv4-comment-stream-header
Provider search http://www.mfrtherapists.com/