I did see this again. Although I'm not entirely sure of why, if there was a single defined problem set *and* depending on the order in which problems were added to the set, then the DB call in WW to retrieve the problem IDs for that problem set were returned out of order.
When a second problem set was created and as few as one problem added to that set, the DB call in the first problem set resulted in a *sorted* listing of the problems and they would appear in order. If that second problem set was then deleted, the bad ordering would reappear.
My hunch is that it had something to do with how the information was cached. However, the sort that was added in the commit listed above fixes this.