You could tell them to try batters and a music CD then it wont matter if it's the wrong PCU and if the "hit or miss" keeps up then it's more than likely the laser going out of if it works every time then check the PCU.
After tinkering with my CDX some more it stopped spinning up the disc so I think the laser was on it's last leg and could see the CD but once it started to spin it would lose the track and try to move in to find it again thus grinding the gears. I ordered some new lasers I hope there here tomorrow.