Reversing light failure (Windsor)

I noticed that my reversing light was not working on my recent trip to Spain (back 1 week). I have checked the bulb which was ok, but changed it anyway.
Now the very odd thing is that it either does/does not come on if:-
1. The vehicle is on the level or pointing uphill, handbrake on or off or footbrake on/off, but in reverse gear, the light does not come on. same if actually reversing on level ground.
2 The vehicle is pointing downhill then the light comes on, stationary held with handbrake, stationary held with footbrake, or actually reversing uphill.
It has been suggested that the wiring done by A/S to extend the cabling to the A/S rear lights in general and the reversing light in particular can be a bit tight and that faults can occur with movement of the suspension etc.
The circumstances described in 2 above would result in the rear of the motorhome body being raised with respect to the suspension.
So just wondering if mabee the wiring is somehow being effected by touching the suspension or minute movement/flexing of the bodywork/chassis.
Any thought or others experiencing this odd phenomena much appreciated. Not been able to crawl underneath at present.
Thanks Mike

Mike,

Almost classic symptoms of a loose connection or a damaged wire somewhere in the circuit.

I know it's not the best weather to get underneath but, "On yer way sonny!"

Best regards,

Ian

Another possiblity, the reverse-light switch may need slight' adjusting' to either the gear linkage or the gearbox itself, usually quite an easy job.