I recently got a refund on my Yamaha micro after going through two units that both had the same fault.
Straight out the packaging the CD tray wouldn't open and the replacement CRM170 they sent me was also lacking right channel sound! After the retailer collected the second faulty unit from me, they said they'd confirm the fault and to be sure test the third replacement before sending that one out. I got a call a few days later saying that their technician had tested their remaining stock to find the same CD tray fault on all of them!
Of course as long as you're buying from a reputable dealer, you're covered by warranties and guarantees but just a word of warning that there's a bad batch out there...