I had problems in shoulders and other joints and I think a lot of this is inflamed tendons but I think I have a genetic predisposition to develop inflamed tendons. Try and dig around that area and feel for a muscle band that is tight. Then keep massaging it until it softens. Another thing I’ve found is if a movement hurts the tendons aren’t moving properly, in my head I see this as the tendons not gliding past each other smoothly. I try and overload it to basically force that area to move Work it until it really hurts and repeat it as much as possible. Takes a month but this has fixed a lot of issues that have come up for me.

I had this issue with Icebreaker sweaters, my first one i bought 10 years ago is in perfect condition but the few i've bought since have all fallen apart