Dermal/Necklace Clipping into neck

Hello, I'm bad at explaining things but I'll try my best to be as descriptive as I can lol; Basically I have this dermal on the neck area that looks perfectly fine in sims4studio and in game when my sim is standing still, however whenever my sim moves in certain positions the dermal sinks into the body so it's like its not even there but it returns when my sims is back in standing position. Idk exactly how to fix it so if somebody could help me out I'd appreciate it.

here's the blend www.mediafire.com/file/lz7pjcb7t3m5uk8/7771.blend