Headlight

after 5 years of faultless service, my headlight have started dancing...

Switching the headlights on allows both pods to rise but they are no longer sync'd.

The drivers side light appears to be fine.
The passenger side pod rises after the drivers side, and it does not stop at the correct point, it seems to start to go back down before stopping.
Additionally, I "think" i got a waft of smoke from back of the dash while i tried the switch. I say think, it was in a dark garage so i can't be sure. Definately no flames though!

They both light up as they should.

Any tips, or clues to diagnose? Basic checks?

Thanks in advance, Hywel