Headlight Earth Issue

Hi all fellow Syncro owners.
Variation on the headlight theme. My lights doing odd things. Work OK on low beam. When I go to high beam the left lights go out completely. Fuses Ok. have a headlight relay kit installed. Swapped the relays over, same problem. Swapped globes and then the entire headlight unit. Same issue. Got out the multimeter. Power to RH side about 11 volts. Power to LH side about 7 volts. Used a different earth location with the negative probe on the LH side other than the headlights and voila, got 12 volts. So it’s the earth connection. Checked Bentley and the headlights go to terminal 30. I believe this is the two round multi point connectors next to the fuse box.
Will do a check and clean but I have seen suggestions of doing another earth closer to the headlights.
Thoughts from the wise heads out there?

Earths are always a problem with these old vans.

The headlights cop all the weather too - especially when driving forward at speed.

I had a high beam that would keep blowing the fuse or globe (cant remember) but changed the housing/ glass of that light and I had no further problems. I couldn’t see anything wrong with it too.

Additional earths are always a good thing.

How did you go Peter?

Any luck with the lights?