For years I've been having an issue with neck accessories. Me and many others asked for a resolution, however nothing has been done. I decided to make this BUG report again since EA seems to be trying to resolve bugs lately.
All neck accessories appear distorted, zig-zagging, chunky, hidden inside the skin, or floating way above the chest. This happens to all female body types and it also happens to male Sims, but the distortion on male Sims is less visible.
I am using a few CC mods (nothing affecting gameplay, just a few Build objects and a few CAS items). For instance, I may download a Maxis-made Sim (e.g., Winnie Harlow) from the gallery (which is CC free) and if I add a neck accessory, it appears distorted like that. As I said, I don't know why, but on some Sims the issue is even more annoying, while on others the distortion isn't as strong and you can overlook it (but it's still there). If I play with shoulder length or chest size, I can see the neck accessory moving appropriately, but it can never look right.
It seems that on extremely fat Sims (max muscle and body weight and big shoulder length) the neck accessories work flawlessly. On any Sim below max weight the issues with clipping begin, with the thinner the Sim the more problematic neck accessories become (e.g., no muscle and low body weight makes the accessories even clip inside the body...)
I disabled all CC and the neck accessories still look distorted. On some Sims it is very prominent, but on others its less visible (but still there).
I also moved the Mods folder to Desktop, deleted localthumbcache.package and tested on a New Save. The issue is still there. It seems to be an issue with Sim weight/muscle. Overweight Sims (max muscle and fatness) have no issues. Any changes to lower the body weight causes neck accessories to become more and more distorted.