FTO AUSTRALIA

Ok, i've fix up the electrical drain problem which was just a simple wire touching the bolt on my rear tail light, now i've left with this annoying problem which the reverse light is on by itself constantly sometimes, but if i put on reverse while the light is on and back to netural the light will turn off

i when to an electrician before but he said it's a mechanic job (under the car stuff), does anyone have this problem before or know how to fix it? right now i just pull out the fuse so no reverse light!