I have the radrunner 2 (2020) and haven?t really had any issues until after the first year. I recently replaced my back wheel assembly in the beginning of this year and everything was working fine until couple days ago I got error code #21? I checked every connection several times and tried my original display that came with the bike but still won?t turn on. I removed the battery put it back on and try to power it up and there?s a slight ?surge? in the motor like it wants to go but the display flashes on/off so quickly and nothing happens after that unless pulling the battery again just to repeat the same issues again. I?ve been waiting for rad to email me back for days now and I?ve been searching the web for similar issues other have had but not finding any thing I have tried already.. any help would be appreciated thank u?