Dealers can be idiots if the person you're interfacing with isn't doing his or her job.
Case in point: just today my F150 needs a master cylinder as one of the primary cups is leaking internally and under a hard pedal (think holding the brake on a hill), the brake pedal sinks to the floor. I didn't think to "demo" the problem when I dropped my truck off for warranty work as a sinking brake pedal seems a self-obvious problem to me when it is followed with a written explanation. Imagine my surprise that the dealer didn't change out the master cylinder because they could not duplicate the problem.
With the service writer in the cab with me, the brake pedal went to the floor. I'm good, right? No, no I'm not. The service writer guy then tried the brakes and said he couldn't duplicate the problem, and besides, the guy says, if the master cylinder was failing the brake light would come on. Huh? I'm a mechanic and so I offered to explain how a master cylinder works and how it can fail like this and not set off the brake light, and beside who cares, what did he think was wrong if the pedal goes to the floor?
He said the pedal goes didn't go to the floor.
Then ensued a 15 minute argument that I lost because the guy walked off thinking I'm dumber than a box of hammers.
Eventually I got people who matter to say, WTF, the master cylinder is bad, but by that time the writer had left for the day.
My point: sometimes the stupid piles up on one person and wrecks what should be a no-brainer issue to fix even at good dealers.