Been in really wet areas? I seem to remember a posters that had similar errors after heavy rains, driving through standing water, that went away when the car 'dried-out'. They had a REx, and running the REx engine for 20-30 minutes seemed to help the drying out process.
Failing that, have read that persistent moisture in the cable connections that won't go away requires changing out the HV cables.
2015 i3 Rex, Capparis White, Tera World, Technology & Driving Assistant, Parking Assistant, Harman Kardon Audio System, 19 inch 427 wheels, EVoInnovate EVSE