Right, I've probably never noticed the fact that ClothCalc automatically updates data after each update. Must have been lucky that I haven't encountered the overload error in these cases before today. My badClothCalc should only automatically request data when a new version (not revision) was released (to resolve conflicts with possible new data formats), like yesterday. Indeed, the last update didn't really require flushing the data cache, but don't worry, after I release the new engine today evening, there will be no server overload anymore ;-).
On the other hand, under normal circumstances, ClothCalc should be able to handle that new pair of black cotton shoes without requesting new data. So if that's really broken, please confirm and we will look into it.
The black cotton shoes were just a random item I used as an example (found them in an iron chest today and thought of them first). I know the calculator doesn't need an update when you find a duplicate of an item you already own.