I have 2 question

I have a 2002 E825 gem.This year when I brought it out from storage I started to have issues.When the ignition is turned off and the E brake is off the display board flashes all Zero’s or what ever level the batteries are at.If I apply the E brake 04 code comes on the display wih the red light on over the wrench.That would be a normal condition if the key was on.When I turn the key on the Gem appears to be normal.I know that this condition is taken charge of the batteries unless I hit the kill switch everytime I turn the key off.I would appreciate ANY advise on this

and the second question

Car has ride 4 fun motor and new gel batteries. Gearbox seems to be a little noisy and regenerative braking causes a high pinched squeal, but the most significant issue is a rhythmic surge when holding a constant speed. Cannot feel a surge during acceleration. Any guesses as to where to look first. Accelerator switch?, controller?, bearings? Constant velocity joints? Any help would be greatly appreciated.