Bad ground

[Shep1970]

Hello, i dont do electrical(dont like it) but my thought would be:
Neutral reverse switch inside case stopped working at some point and someone bypassed it?
Now maybe years later their fix has come apart(wires)?
Now you come along and put everything in its place.
Is there an inside case (switch)?
Internal switch that tells cdi to fire or not (neutral,or in gear) think i'd test that first. Thats all i got. Just trying to help
Neutral light on when in gear would tell me switch.