Strange Headlight Flicker Issue

[Best4x4xFAR]

Began noticing intermittently that both the HID Headlamps will go out for a brief moment (less than a second) periodically. Seems to happen ever few minutes.

Now last night it was dusk, and I was driving with the running lights and the fog lights on, and each time I would come to a stop, the foglights would go out (Not immediately, but maybe 2-3 seconds after coming to a complete stop). And they would come back on 2-3 seconds after I started moving..

Putting the truck in neutral (so I didn't have to have my foot on the brake), didn't change anything, nor did coming to a gradual stop with the truck in neutral using the parking brake.

After turning car off an restarting, can't seem to duplicate the foglight issue now, but still having the periodic 'flicker' of the main beams.

It appears to be both headlamps at the same time, so I don't think it is a bulb (recently replaced OSRAMs) or a ballast issue...

Some searching on the web seemed to indicate a short in a tail lamp could cause the flicker, and I have a bulb socket in the passenger rear that can be finicky, but it has been fine lately. Would unplugging the entire tail lamp cluster be a good test if that is the issue?

Any other thoughts?

(Beginning to wonder if it is worth sinking a bunch of money into overdue maintenance/leak fixes - OFHG, Valve Cover Gasket, Thermostat, water pump, belts hoses, CCV, O2 sensors, etc)