Odd "spikes" in distorted mesh. Need help.

Hi. This section of the forum is meant for helping someone fix the issue they encountered with s4s or the process of preparing cc for s4s, not fixing it for them.

The issue is caused by the choice of the maxis item to start a package from. The dress you cloned, yfBody_DressRuchedParty, is too short to be affected by skirt bones but your dress is long enough to have them. So by importing your dress in that package you introduced new bones.
The solution is to clone a longer dress made out of three meshgroups like yours is.

Also, its best to delete all bone_bone_shape.00x and all rig.00x. Leave only the original rig.