Vauxhall Vivaro B 2016 Tail light relay

[Tezz]

Both tail lights come on briefly then go. Suspect a relay but not sure which one as the books is bobbins. Anyone have any idea? 

 

JFYI - Reverse light and fog light not working either.b

[Vauxhall Owners Club]

I would be looking at any earth connections and leads in the rear of the van to start with
Clean the earth points or substitute some earth leads directly to the lamp unit(s) to see if that improves it