What was the problem? If the local repair center couldn't reproduce it, what was going on?

And what do you mean they lost your return? Like it got delivered and then it was lost? Surely they gave you a working unit at that point?

I've had a bunch of experiences with Apple repair and always always been fast and great. I mean, they're definitely the best service of literally any corporation I've dealt with, by far. Sometimes you get unlucky I guess with a particular rep or something hard to reproduce, but it sounds like you got extremely unlucky? It definitely isn't representative in my experience, not even close.