hi i solved e01 err [well in this instance anyway- unless there is still a prob with motor drvr's etc.] try split the case into its 2 halves reassemble -- err msg gone -power or gnd link at front of case lower down is split and rejoined by the above procedure - perhaps this causes the s/w reset.

The GR-DVL520U and the GR-D30U have completely different mechanisms but the code is the same, E01 is a loading error, it can be caused by both mechanical and electrical issues. I am a technician that has repaired both models and others made by JVC. The codes that come up are to point the technician in the right general direction. An example of this is your E01 code, E01 is a loading error, it could be bent, jammed, or damaged mechanical parts, sand in the worm gear on the loading motor, a bad loading motor, poor electrical connection on the loading motor, bad driver IC, bad control IC, problem with the mode switch, and the list goes on. So you can see that E01 and other codes are not as simple as it seems on the surface.