You said you think someone has been into the wiring. Can you show or tell us why you think this?

Can you send a picture of the wires going into the relay?

I am hoping the wiring has been messed with and the colors are off.

I am starting to think, like cab, that you have a wiring short but a picture of the relay and wiring may help.

Did you check to see if the reverse light stays on through all the gears?

Do you have a voltage meter? A regular test light?