Sounds concerning. My C01S hasn’t arrived yet but all of my original Yuji C01 are perfect.
What you’re describing sounds similar to mine. I suppose it’s less than perfect, but seems acceptable to me.
Yeah, I’ve seen the “barely off but easy to turn on by wiggling” thing happen with several kinds of little AA twisty lights.
A nuisance if it happens in a pocket. “Why are your pants glowing” isn’t the kind of question a flashaholic appreciates hearing.
“Less than perfect” is an apt description.
It’s certainly still usable, and I do tend to be picky. However, I didn’t notice anything indicative of a manufacturing defect. The clip on mine broke when I was trying to remove it, but that’s another story.
Muggles might be especially frustrated by the behavior. The Olight’s functioning is more as I would expect.
Note that it doesn’t turn on accidentally even if I try to wiggle it. If twisting more than 2mm past off, there is no problem. It’s really only in a small but critical region where I notice the flakiness.
Similar to mine. I’ve just adapted to it and turn it tightly each time without thinking about it. My old Fenix e01 has even more ability to turn on by pressure to the head, but it doesn’t need to be tightened all the way to turn on like the C01s. I think I’ve overlooked this minor imperfection because of the nice sst20. Thanks for reminding me. EDC01 has a butter smooth action that works well.
Maybe it has something to do with the bezel not having a hard stop when tightened over the pill, and no glue. You can’t tighten it very hard because then it goes so far over the pill that the light does not switch on anymore. So twisting the head to switch on the light also moves the bezel a bit, twisting the light off may even screw your bezel off the pill. A drop of suitable glue under the bezel may make the switching more reliable.
Just get an EDC01
high CRI b damned 
drewski Yes, I really like the SST20.
That description doesn’t sound anything like the C01S. The bezel isn’t loose, and head definitely can’t be tightened too far, since it screws flat onto a ledge on the tube.
I wonder about wear on the PCB’s metal contacts that rub against the tube, and the center contact that rubs against the battery head. They do leave slight marks, so I hope they don’t cause contact issues later.
Bearbreeder I’m surprised at how much I like high CRI after experiencing it in person… gonna be hard to give it up now 
Keeping the threads lubed will help.
I noticed that on mine, and it was due to the outer reflector ring being slightly loose. Overtightened that so it wouldn’t get loose again, and it was stable. I have five of these now.
How would that help when the issue seems to be due to play in the threads?
Do you have a picture of what you’re referring to? I don’t see anything loose on mine.
My keychain flashlight nowadays is a EDC01 with a led swap, a sst-20 4000k 95cri
@phouton my Sofirn C01( with high CRI Yuji) had the same problem you are describing! But then i lubed it a bit and “voilà” problem solved.
I’m confused how that could help.
What common household products are good for thread lube?
I will add that my C01s seemed unlubed and was squeaky out of the box. It was much better after some lube and pulling rubbery stuff off the sides of the contacts on the head.
I like Syl glyde. Maybe not “common” household stuff but well worth having on hand.
Without thread lubing is harder to go all the way down, preventing a good contact! I use Xtar X-lube (Silicone grease), but probably you can find something similar in a local hardware shop.
Oh, I see. Mine has no problem going all the way down to make contact. As I described, the issue happens before it is fully screwed in.
If it has trouble going all the way in, I’d think that would indicate the O-ring needs lubrication, more so than the threads.
The threads and O-ring on mine were very slightly greased when I got it. Not much, but there was definitely something on there. I’ll have to check if we still have some automotive silicon grease lying around.
I just use silicone electrical connector / bulb grease from the auto parts store. It was $2-3 for a small tube. It only takes a little bit on the o-ring, so a small tube lasts a long time.
Yeah ... was gonna say lube . .. sometimes wonder if threads really need lube or if it's o rings only. I usually lube threads and then wipe them clean so they are slightly lubed . more generous on o-rings and more so on twisty lights .
I used some silicon lube from a spray can applied with a paper towel onto the O-ring and threads. It seems less viscous than whatever was already on there. The result is just that it’s easier to screw all the way, but doesn’t change the finicky behavior. If anything it seems I really need to screw it down all the way now, since with the O-ring more lubricated, it allows the head to move more easily.
I suspect this is just due to play in the threads. The head has to be firmly screwed in so that it is seated onto the ledge in the tube, otherwise I guess it can rock. The contacts are on the bottom surface of the PCB touching the ledge, so this can cause them to make/break the connection, causing flickering or cycling through modes. At least that’s my current hypothesis. I imagine this is why contacts are often designed as springs.