I was going to suggest double checking both ends of speaker cables for a loose strand, but the above amazon review suggests some sort of QC issue. Too bad about that, but I'm sure every single brand has at least 2-3 out of every hundred sold have defects.
Still, it wouldn't hurt to power up the yamaha with absolutely nothing connected to it( volume at zero) to see if it still goes into protect. If nothing else, it'll be extra results to give to the dealer.