What battery are you using? Maybe it is pressing hard to the switch. Cleaned it throughly yet? It's almost a requirement for all budget lights.
Is that with a protected 14500 or an unprotected 14500, or is it an AA?
Some protected cells are too long to work properly in some lights.
Can you make it not work when the tailcap is off and measure the current draw? I worry that when it is fully tightened you could be getting a dead short (positive and negative ends of the battery are being connected) possibly by the metal reflector making contact with positive and negative points on the LED. If you can unscrew the pill from the head maybe you can see what kind of protection is between the reflector and the LED and possibly improve it. Usually it is a white paper disk with a hole in it for the LED.
It may be that the problem is a switch retaining ring that needs to be tightened. This is not unusual. It sounds to me like the internal length is not adequate. If the switch or pill have climbed up their threads, this will make the light too short internally.
Take off the head and tailcap and shake them gently. There should be no rattling at all. If there is, you have found the problem.
This is what they should look like.
Head. If the head rattles, you need to tighten it up. You can see there is a slot in the edge of the pill that screws into the head at about 11 o'clock. There is another slot 180 degrees opposite it. A fine pointed pair of scissors or a pair of circlip pliers will fit in there and allow you to tighten it up.
If the tailcap rattles, you need to tighten up the switch retaining ring.
Here's the inside of the tailcap. There are dimples in the retaining ring which a tool can be inserted into to tighten it up.
If they don't rattle, it sounds like your body tube is too short. I'd try a different AA cell just in case though.
Oh, and by the way, welcome Lewis. It's good to have you here.
Don't overtighten it.
Nothing in a torch needs King Kong force normally. Think tightening down sparkplugs.
I would have thought the pill to be loose and when compressed by the battery it would push the pill hard enough against the reflector to short out the emitter on the reflector due to the poor paper washer insulator.........or It could have been the clicky being pushed into the bottom of the tailcap too hard and causing the clicky to push against the rubber post that actuates the clicky just enough to shut off the light.
Like Don said don't King Kong tighten anything and trim a small bit from the rubber post and and cut yourself out a nice insulator from a butter bowl lid to put between the pill and reflector and you will be good to go!!
Hey Don is that a pic of your 93mm C3SS head and driver? If so It is different from mine I got at LighTake.
Yes, but I got it several years ago. I think it was in 2007-8 when they were first announced at DX that I bought it. Never regretted the purchase.
I ordered the Skyray S-A1 from Lightake a few days ago and it looks like it uses the same driver as your C3SS. I viewed the driver pics elsewhere on the net though as Lightake didn't have any, but you do get a glimpse of the driver in the video. I thought the pads might be programmable on the S-A1 like the AK47 but after seeing the pics of yours I can see it is just contact points. Is your C3SS 3.7V tolerant? Mine is not!
Skyray S-A1 eh?
I have one. It's a woderfull light with decent brigtness nice tint (your may vary) nad perfect mode memory. However it has a drawback. When the AA alkaline cell reaches 1,29V it starts being nasty. Mode change dosen't work properly, often does not even switch on. Unscrewing the tailcap and putting it back (just to disconnect the circuit) then works fine for a few minutes again.
With full AA's works perfectly.
I have read where you posted about that problem. If they all have that issue i'm going to see if I can fix it. I assume it will have something to do with the stabilizing capacitors not being high enough value to deal with the voltage drop causing the circuit to go unstable or it could also be a reverse polarity protection diode dropping the voltage too much. I will make a new thread and post my impressions and results when I recieve this light. I am waiting on 4 lights right now! 
ultrafire c3 are easy to fix, its not the tailcap.
You need to solder a ball of solder on the head of the flashlight.