There have been two instances that I can think of:
1. One was in the MAX thread right here on Head-Fi. He's a frequent poster in many sections on Head-Fi, but declared his unwillingness to work with fixing the mistakes or accept help.
2. One was on DIYForums.org, where the user posted a pic of his populated board. Unfortunately, we noticed that the output transistors were reversed in a couple of cases. Despite numerous entreaties and even a few PM's from myself and ruZZ.il, I believe, he was never heard from again.
Both of these instances are a real shame. AFAIK, there has not been a single instance of an unsolved problem with a MAX for someone who was willing to accept some help.
It's well known amongst many of us, but one user (Amphead) personally took delivery on an entire balanced version of the MAX from a user and fixed it. Even so, that was the only case I can think of that was not solved from just posts and pics in this forum and on DIYForums.
I'm sure there are several of us who are willing to do that if all else fails - but the builder has to have the desire to fix it, first.