Surely the lever wont go faulty in both directions?
You checked all the easy stuff like fuses earth straps etc.
Sometimes they loose one direction due to bad contacts in the lever and a bit of WD40 usually does the trick.
Also worth double checking the connection blocks going to the lever for bad/corroded connections.
Something simple when you have nothing, safety switches are ok?
Welcome Bounty might be worth posting this in "Talking Tackle" if you want. I'd give you a hand but am listening to the radio, cant do everything ...