arms gravitating into sim in CAS and in-game on new mesh?

i've encountered an issue with a mesh that i just finished. it seems that the sims' arms are gravitating inwards and clipping into their body with the mesh. i checked the weights and nothing was out of the ordinary. not sure what is happening. the arms just kind of sway back and forth but remain stuck to the sides of the sims' body. here is what it looks like in cas:


any help would be appreciated
here is the .package file: simfileshare.net/download/148343/