TacticalBarbell.com

I don't know if this will help anyone, but I've been dealing with a sore shoulder for the last 1-2 months. It didn't feel like an injury, just achy. I was doing some online research and watching some videos and Allan Thrall said something about how often soreness in one muscle can be attributed to tightness in a contrasting or connected muscle. I started feeling around on that side of my arm/upper body, and I found a lot of tightness in my bicep. After 2 days of foam rolling my bicep (and it was painful!) and a lot of stretching, my shoulder feels 10x better. Again, I don't know if this will help anyone else, but that's been my experience the past couple of days.

I have had similar experiences with biceps stretches.
Issues with the shoulder can be a lot of things to be sure, but a common denominator in a lot of people seems to be excessive tightness in the dominant side and "forward hunched" posture.

In my case i struggled with this shoulder issue for months until i started stretching my biceps and doing band pull-aparts..