Thanks, Justus. Usually they do give error codes, but the toyota we had should have too and didn't, so maybe this could be the same.
Yes there is a encoder bearing but it should give a error code.
Thanks, but don't think so. Battery is definitely not the worst we have seen, voltages and gravity ok, connectors ok. Truck drives well too, despite the wiring issue. Is there a speed sensor bearing on the lift motor? We had a toyota recently with a drive motor sensor bearing fail, this didn't show a fault, but drove very slowly.