I have this too, for both the weight and the muscle. It's been that way in my game for quite awhile, it's not a new thing for me.
When I use the gallery/library, and place a sim into a house, then in live mode their sliders have reset to the middle. I go into cas.fulleditmode and change them.
Recently, I had a "simself" party, and downloaded a large amount of people's character. THey all went to 50/50! I had to start over, take a picture of their sliders, then go into their house, bring them back into CAS and adjust it back.
It does work fine as a workaround, but would be nice if I could avoid the bug in the first place.
