Have to agree with BB on this, A bug report is the way to go, and now might be a great time for it, the cloth and hair rooms in Poser seem to be lacking in the new DAZ studio and ANY improvements in those areas might be welcome at SM. Also grab your friends and if they see the same results have them also post official reports, numbers sometimes help.

 

In the meantime if you are working on a still frame render you might try using the morph tool "smoothing" function set at VERY small strength after you finish your sim, sometimes this will relax the vertices and fix the problem, however over doing it may loose the fold, so go slow.