Short answer. Rad Power error codes appear on the LCD as Exx. E02 is a throttle fault, E03 is a controller communication error, E04 is a brake lever fault, E05 is a motor hall sensor error, and E30 is a display communication error.
Step by step
Identify the code. E02 throttle, E03 controller comms, E04 brake, E05 hall sensors, E30 display. Write it down and note when it happens.
Check the reported connector. Rad errors are almost always a loose or corroded connector. Trace the harness from the display down and reseat everything.
Test in a dry environment. Rad harnesses take on water at the connectors. Let the bike dry fully in a warm garage and test again.
Replace the failing part. Throttles, brake levers, and hall sensor cables are cheap and stocked on any good mobile van. Controller swaps are the biggest fix.