Move your Mods folder to the Desktop and delete localthumbcache.package. Then test the game in a new save.
If it works now check for updates to your Mods and CC. Add it back a little at a time while testing until you have found all that are broken.
I moved the Mods folder to Desktop, deleted localthumbcache.package and tested on a New Save. The issue is still there, exactly like it is in my lightly modded game.
All neck accessories STILL look distorted. They only look alright on extremely overweight Sims (max muscle and max weight). Any changes to the sliders below max muscle/weight and the issues with neck accessories begin. On Sims with no muscle and low body weight the issue is ridiculous. Accessories are all crooked, zig-zagging, buried inside the skin or floating above the chest.
So I doubt it's a mod issue.
