It would be much better if designers were given a couple of days grace period to fix issues identified in the manual pre-print checks before cancelling an order. An immediate cancellation may be easier administratively, but it does nothing good for the relationship between the designer and potential purchaser. A customer who has had a print order cancelled once is unlikely to re-order from the same designer; they'll feel that they've been messed around, and will go else where with a negative impression. That's a regrettable situation, especially when a model might be fixed with just a few minutes work.
Another thing would be if you had an option that you could check on each model that would allow them to automatically run a "FIX THIN WALLS" on any model that doesn't print properly instead of simply cancelling the order if it doesn't print properly the first time! Would save alot of time and would keep customers happy!