Yeah, that "we can't duplicate the issue" is typical at all dealerships and most brands. I've had to do exactly what you did with a leaking windshield, had to drive in there during a torrential rain storm, since all their leak detector personnel couldn't duplicate it with a hose. That's why when people talk about exotic cars, cars where there may be one or 2 dealerships in a 300 mile radius that can service the warranty stuff...I always gotta point out how rough that can be if you can't get things narrowed down on the first few tries. It's not uncommon to go back to a dealership multiple times over this, but the flip side too is they can't just replace parts and bill the manufacture without clearly observing the issue, as they could be audited for fraud on a regular basis and be big trouble, may be fined or some other punitive thing they do...