Yes, the site gets LOTS of offers and this is the ONLY customer that has seen the error.
So, my guess is that it is an extremely rare glitch (and as one programmer to another, we both know how extremely hard, if not impossible, those are to find and fix.)
My first thought was that it was because two offers were approved, and somehow that reset something. If you aren’t having the problem with two offers from the same person approved within a minute or so of each other, then I have no idea.
Can you think of a place in your code where I could add a “do_action” and what values I could pass to it where this might be occurring? I could use that to detect if it happens again and provide more information to you.