Eyc headlight problem

On last night's ride I took the touring bike with its B&M Eyc headlight
powered by an old Union bottle dynamo. (Usually I take a bike with a hub
dyno.) The Lumotec Eyc is about 2/3 down this page:
https://www.peterwhitecycles.com/b&m-hl.php

My friend who rides with me often leaves his headlight off to save his
battery, since we can see so well by mine. But not last night. Right at
the start, my headlight turned itself off. I tried the switch (and I do
dislike "soft" switches buried under rubber covers), I felt the wiring
connections, spun the wheel a few times, then it came back on. Rode ten
feet and it blinked off. Then back on and stayed on, mostly, but would
occasionally blink off then back on.

At one stop to listen to a chorus of frogs, the Eyc was running only its
standlight when it suddenly blinked off. That tells me it's not a wiring
connection or an internal dyno problem. It must be a problem inside the
headlamp itself. Also, it's not triggered by bumps AFAICT, and it
sometimes blinked off while riding a perfectly smooth surface.

Fortunately, it always came back to life and for the rest of the 15 mile
ride it blinked out only occasionally, and for never more than a second.
But its very worrisome.

I'll be writing to Peter White, from whom I bought this. But I'm
wondering if anyone here has had similar troubles with a B&M lamp, or if
anyone wants to get a head start on speculating.

(When my electronic poltergeist starts infecting my bike equipment, it's
a bad, bad sign.)

--
- Frank Krygowski