Well, the obvious answer is that Alhazred should go ahead and give the jetpack to Dorian, and I should figure out how to fix this right-quick. My guess is there's a few seconds of overlap where the auction is about to be processed, but where it still lets you bid even though it shouldn't.
Okay, I think I've got this fixed. There was a window where an auction could be ended and marked for processing, but still get bid on. Should be covered. Thanks for your cooperation, Alhazred. I realize that's a little goofy for ya.