I've gone through a bunch of these. I gave a half dozen 'seconds' away last Christmas. They were the original switch (no click for on). I considered them 'not broken' then, still do. You sometimes had to fiddle with them to get it back on or to stop flickering. It's a flashlight, sometimes they flicker. To a guy that's lived with Lucas electrics in British cars this is normal......
I still run a couple around here on NiMH cells. Yes, they're dim (but often plenty), yes they might be dead or die quickly but there's freshly charged cells at the ready. Suitable for many uses. Ignoring the small cost of electricity to charge the cells (no I haven't set up the solar charger, yet, but I'm collecting the bits) and given the lack of a conventional bulb to replace, they're free light, right? But they are at their best on the Li cells.
The Reactor III is a different matter. Generally very good performance on NiMH, a 'first choice' in this house. We have two.
I've also cut up a few of the $15 ones and pulled out the $15 LS-O with it's neat 'old style' optic. When you do so, it's easy to see why things might flicker. The light depends on a sliding contact against a slot milled in the side wall for negative contact. Has to,. the LED moves up and down within the head as the power is turned on and off. It can also get intermittent if the end isn't screwed securely down.
Again, I guess flashlights have always flickered from time to time in my lifetime. I might even say that my Arc LS and the others that I own that haven't yet just haven't yet. For sure I wouldn't fear it 'packing it in' when camping (although I might have to fiddle with it), it far far more reliable than it's predecessors.
Doug Owen