Yep. Good answer! A bit more research determined the problem to be moisture related. It self resolved by the next day. It's concerning as it hasn't been near water yet. The Reign is my second Giant Ebike. Water ingress killed the first one (RIP) so I'm sensitive to this..
Did you get a solution or determine what causes both rows of LEDs to be fully illuminated white with no power to motor and unable to switch off? I have the same issue start today but pulling battery does not solve it. The issue persists.