Hi Tim,
Not familiar with that code; I have not had any issues with the depth finder. Did you try cutting the power from the main battery switch? Then restart the E-80. I have no doubt you are doing it this way, but the start sequence is: Depth Finder, Autopilot, then the E-80 and the VHF.
Look at the backlight around the large round knob to make sure the power is out to the main unit after shutting down.
In researching this, the only thing I could find regarding the Watchdog Timeout Reboot (first I've even heard of this) was that a firmware update from Raymarine may be needed. (from The Hull Truth forum)
Let me know if there's anything I can do from this end.
Best wishes,
Jim