If you suspect it's the power, there's a USB 'Y' cable you can get that enables you to plug one into the CDJ port, and the other into a power source like a smartphone charger (these typically have a high power spec, 2amps is the target, FWIW.)
Otherwise, I'd suggest running CHKDSK on windows or similar tool on mac. The CDJ's are pretty 'chatty' with keeping sectors open on the disk and if the device is unplugged or powered down before the stop procedure, it will trash both the open sector along with the file allocation table, rendering the device effectively corrupt. This can also happen on the computer, too, but modern OS's are better behaved about queued writing behavior so the only times you'll likely see this is if things get killed in the middle of writing a file out to disk (like copying a file, editing tags, etc. and the cord gets yanked.)
