W211 Bi Xenon flickering

[Lyserman]

My nearside headlight has just started flickering.
Those that have fixed this, was it the igniter unit on the back of lamp or the control unit under the headlight?
Is there a way of diagnosing without replacing various parts?
Many thanks all.

 

[Major774]

I would try swapping the bulbs around to see if it's an issue with the bulb itself.

 

[Lyserman]

Did exactly that.
Turns out to be a faulty lamp. It went yellow as well.
Fortunately they were not that old and having bought them from Amazon they are being replaced under warranty. Great customer service.
Osram Nightbreakers for info.
I hope these new ones last longer.