Muscle spasms - post radiation?

I get them too on my left side , shoulder and around to my back. Mainly reaching for the remote after sitting for a while! I also have very sore ribs on that (radiated) side and have had CT scans to check out the bones there and all was good. My surgeon calls it radiation change . My physio tells me to do the seated twisted and arm exercises and it goes away for a while but comes back. I also find that some of my yoga poses aggravate it........or maybe helping it by stretching it ..........who knows??? :) I did have a wonderful massage  before covid struck where she used a coin to scrape the tissue away from the ribs . A Chinese method. Your skin becomes grazed and red but that is part of the healing process and it gave me great relief , I'm hanging out for another one! Take care!