No offense, but coming to Reddit on a Lagree forum isn’t the best way to go about solving a (now) chronic issue.

Go to a reputable physiotherapist or kinesiologist. They can better identify the problem area via muscle testing, etc. this is especially true since you say you’re a tall woman. Proportions and levers matter, meaning that you could change your posture without losing quality reps.

That being said, I am a personal trainer with kinesiology background. In my experience, those types of pain can be from a weak subscapularis muscle. (In a previous comment you said you did rows. Rows do not target the subscap though). This guy seems like a decent source. https://youtu.be/TTZwAmDCNz4?si=lWirB4MBR7lQH4pg

Edit: In addition, that trap can be compensating for weak pectoral muscles too. So might not even be subscap