Xenon - high beam OK, low beam not working

[E53inLA]

Hoping someone can shed some light on this problem...

Drivers side low beam stopped working. My mobile mechanic & I have tried:

1) New Xenon bulbs
2) New amber turn bulbs (as long as the assembly was out, we figure it prudent)
3) swapping the ballast, left to right, and a used one I got on EBay.

At one point today, when we temporarily reinserted the assembly, after swapping the ballasts, both low beams were working. Since we didn't reinstall the plastic retaining cage for the test, we had to remove the assembly, reinstall the cage, reinstall the headlight assembly.

After putting it all back together:

Passenger side works fine. Low beam is on. High beam works on both positions, turn signal works.

Driver side:

Low beam not working
High beam works on the pull-to-driver position, but not on push-to-dashboard position.
Turn signal working

Any help/suggestions greatly appreciated. (and I did search first, but didn't find anything similar)