That's peculiar ... I've never notice any flickering on any of my Foursevens lights.
What you are describing is different from moonlight flicker (which results from trying to tune a particular constant-current circuit too low for a stable current). In those cases, apperance of flicker is idiosyncratic - some lights show it (consistently) but most lights never do (consistently). In cases of persistent flicker, I would personally return for a replacement/repair. One manufacturer actually managed to re-tune a particular light and ship it back to me once, to resolve this problem.
But the consistent appearance of flicker at specific drive levels and input voltage (across multiple lights) suggests that one of the common circuit components is not able to consistently meet its rated specs. I have seen this occur several times (usually on new model launches). The usual response from the manufacturer is to isolate the problem and find a different supplier for the affected component, to ensure consistent quality. This can sometimes take a little while to isolate, as the fault doesn't show up in every unit (and may not be caught by stand QC processes, which don't test every light on every voltage source and level). But it would indeed not be a good business practice to ignore it.
In this case, I suggest you contact Foursevens directly in the US. It is generally not up to the manufacturing plant to resolve these issues on its own - that typically comes from a directive from "head office", so you should really let them know of your issue. Good luck!
Mine is not the common PWM flicker. in fact It has a very subtle flicker as if when contact point or screw thread is dirty. I try to clean all contact point and screw thread and re-lube it and problem still persist. And when contacted the manufacturer, the engineer even assemble a new unit for testing. And the only reply is: "We tested on our side and we have the same flickering problem, and we have no idea what is cause".
Out of curiousity, I've checked online and found there numeral reports about flickering problem with Quark AA at different mode level, and some of them even dated back to 2010. Here is one of them:
1)
http://www.candlepowerforums.com/vb...Quark-123-2-problem-with-barrel-thread-length
2)
http://www.amazon.com/dp/B00513DDMS/?tag=cpf0b6-20
There are even more cases but I just have to find it again. Some of them contacted 4sevens and all 4sevens do is change the switch and the problem didnt go away. So I am sure 4sevens knew about the flickering problem 3 years ago, and they still didnt fix it in my new unit, which was produced after their so call "rebrand" campaign. And beside the flickering issue, the pre-flash is still there, in all my Quark light. So.... really dont know what to say.
I didn't contacted 4sevens directly because I am currently located in China, and if the manufacturer here cannot fix it, I don't think there is anything 4sevens can do from US. And beside that, there are other brand and model I can get here, so even though I really like the mode spacing and runtime of this light. I just returned the light, and never look back.
Note: If all your Quark do not exhibit the same flickering issue, I suspect that the manufacturer may be using the old batch of drivers which was rejected by 4sevens and sell it here in China. Since all the Quarks here (Not Quark Mini) from both manufacturer and dealer are having flickering problem. And yes, the dealers here tested every single one he have in stock and they all flicker, even the one assemble by the engineer himself.