Whenever I work shoulders and chest I tend to get either a stinger or a numb feeling in my upper back musculature, I have tried keeping my shoulders down when doing shoulder work to keep the shoulders doing the work and also shrugging when I do my chest to make sure I work the chest proper but it doesn’t help, what am I doing physically that causes the stress to hit that area of my upper back?
I have something similar. Is your upper back fairly tight/knotted? Its likely just some muscle/tendon friction, have your chiro look at it.