I still have to take a look at the book but...
If 3373 really is the error code, Maybe you have a bad display panel? Do you have a handset? Assuming the 33 is a malfunction. Maybe the code is a -73?
-73 would be the GE code for a defective RB contactor. It would give you the PMT (pulse, monitor, trip) condition you are experiencing (the jumping). If a EV100LX (or newer) truck does that jump, it absolutely should display an error code.
Does the truck have regen? If so check that the regen contactor pulls in when the truck turns on (it should drop out when truck goes into regen). It has to be closed for the machine to run in normal forward or reverse.
Check that it isn't dropping volts across it when it's pulled in and that the tips are good. Check the wire at PA6. It connects to the A2 connection to the RB contactor. Make sure all those cables and wire are tight and have a good connections.
A few different codes will cause that jump. Defective RB, F and R contacts will throw a code (code 24 for directional contacts). Lose cables can look the same to the EV100 as bad contacts. Where are the sparks coming from?
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.