As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT ON RAMP, APU WAS SHUTDOWN AFTER RUNS AND ADG AUTOMATICALLY DEPLOYED. THIS OPERATION SHOULD NOT HAVE HAPPENED UNLESS ACFT IS IN THE AIR. TROUBLESHOOTING FOUND THE CONTROLLER FAILED. RECOMMENDED REPLACEMENT TO CUSTOMER AND THIS WAS ACCOMPLISHED. UNKNOWN FAILURE INSIDE BOX, UNABLE TO DETERMINE EXACT CAUSE.