I didn’t read every reply, so don’t know if this has been asked, but is it a cellular version?
I have had a few problems on and off with sensitivity with the watch, specifically when I bought a 2nd gen SS some years back. At the time the watch was thicker, and the sensor seemed to hit a specific nerve in my arm, causing shooting pains up my arm - didn’t happen with the regular aluminum, so that’s what I’ve worn since, and didn’t get cellular version again for several years (Until series 6, and now 7). Occasionally I have what feels like a slight burning sensation, but I can turn cellular off for a while, or even remove my watch for a short time, and it subsides. It doesn’t happen all the time, so I’m fine to remove it and take a break from it for a bit if needed.
I did try going to a SS again with series 7, and, though I didn’t give it much of a trial period, it felt fairly quickly like it would be more bothersome to me - I just think that little extra weight must be enough to aggravate that nerve it sits on.
I wear my watch a little looser than most I’m sure. If I need it to get specifics like O2 or do an EKG, I’ll tighten it for that purpose then loosen it a notch. It still keeps up with my steps, exercise, and usually my heart rate with no problems being slightly looser, and that definitely helps with any nerve/shooting pain.