A 502 Error on the Philips DOM indicates an error has occured during the writing to the MMC (device in USB Mode).  Sometimes, this will also display a 503 error.  It’s the same thing.
Recommended Fix:
Format the memory card. If that does not correct the problem, insert a new memory card and format the new card via the DPM device (rather than the Windows format function). (Contact customer support if the defective card contains files that need to be recovered.)
Verification Source: In-house testing