@ksdm From your history, it sounds like you have eliminated spine related causes. Have you explored mineral supplements like magnesium? That does help muscles relax. Here is Mayo's information that also lists things like thyroid problems that can cause muscle spasms or dehydration that can contribute.
https://www.mayoclinic.org/diseases-conditions/muscle-cramp/symptoms-causes/syc-20350820
It sounds like a frustrating issue and it must keep you awake at night.