I zeroed in on such a problem, example, when hmann's crop top is used and the arm begins to contact the side of the top, this is when the sim fails. Hmann has said in his tutorial that one must constrain these vertices in order to avoid this. If this is the reason that sims fail, then it seems that it would be best if (in the case of strappy dress) that vertices around the shoulders and trunk need to be constrained in order reduce the chance of catostrophic collision. The bottom of the dress should remain "as is". I'm not real sure how this will look, but I guess it's worth a try. However, in the case of crop top, I have not even included the shoulders in the collision list (just collars), the cloth never overlaps, and still the sim crashes just as if they were included in the calculation. Note: this is just on a walk. When I go home I'll try a few things and post results.