The symptoms are quite similar to warming up (and the expansion causes some connection to dis-connect) and cooling down (which causes the same connection to re-connect). But I’m afraid that this drop-in is potted. One of the features of his current P60/D26 style Drop in Module with Nichia NVSU233A U365 UV led is: Thermal epoxy.
You could ask the seller if he has any solution.
Or buy a modern light like Convoy S2+ UV 365nm, that driver is so simple hard to fail at all
I emailed seller, he would not help at all.
Finally, this is the 'professional response' I got from the seller, 'CustomLites':
It sounds like a response to a not so nice email that they got from you (but is not shown), or else that he was not having a great day to begin with.
But apart from the tone, and from CustomLites written warranty statement, from a builders point of view he does have a fair point. UV leds are a sensitive type of led that do not like to be driven very hard and are known to fail/detoriate much sooner than white leds. If I would sell such drop-in I would not like to warrant it for years (but I would also warn about the sensitive nature of UV leds). Maybe yours does have a fault and failed without heavy use and without ever overheating, but the builder has no way to know apart from what you tell him. And he clearly is not the type of seller “lifetime warranty no questions asked”.
Well that pretty much says it all. This does not lead to a solution you would like.
The short version of this response is: if you want to last something for ever, don’t get it out of the box.
The language used indicates that the warranty on your light expired a long time ago, in a galaxy far, far away.
The best thing you can do is buy a Convoy S2(+)UV when that is up for sale.
The next best thing is to buy a cheap UV drop-in from FT or KD.
In principle I agree with Henk. If a CustomLites drop-in is not bomb-proof anyway, you may as well get a cheap KD drop-in. The Ledengin led was a bad led anyway, very expensive, big die that was even badly centered, lots of visible stray light. There was not much better at the time, but nowadays there are much better 365nm leds.
Edit: a quick search does not find a P60 drop-in that uses one of the better Nichia, Seoul Viosys, Luminus or LG leds, so the best is to have someone (other than Nailbender 
) make it for you.
It appears to be a thermal issue and not a defective component. If the board is potted with epoxy then troubleshooting will be difficult until the epoxy is removed. Epoxy has a high thermal coeff of expansion, it moves and grows quite a bit due to temperature change.
There is likely a bad solder joint that is being pulled by the expansion of the epoxy which is causing the circuit to open.
If it works for brief periods to scan currency then it may still be useful to you; if you need a longer duty cycle and the cutoff is not acceptable, then it will need to be repaired or replaced.
Who does repairs? seems to be plenty of smart guys on this forum.
repair with a 10 pound hammer —> get a good light or drop in with a modern LED
So they sell products at a premium price with no support after 30 days?
Best is to get a Convoy or similar light its dead simple ON/OFF, you may even replace the driver with one with same AMC amount and modes running biscotti
Or even go with a Bistro driver that can thermally throttle when the light gets warm or hot
@djozz
Yes djozz, your intuition is very good, my email to them was a bit 'frosty', because it wasn't the first time that I emailed them about this problem.
I do understand they have a '30-Day Warranty'.
All I asked was if I could pay for them to troubleshoot and/or repair it, as it was not a budget lite, or at least that they give me a clue or a little help where to begin to look for the fault.
I didn't ask for a life-time warranty or a free repair or replacement.
All I asked for was some courtesy and a reply that was 'Professional' from a builder that sells not-so-cheap lites.
djozz, you're 'The Man', THANKS!!
ConvoyS2+NichiaUV365mm
Okay, didn’t directly think about a third option. How about THIS.
https://illuminationgear.com/products/sportac-p60-led-module-two-mode-incls-adapter-ring
It comes in all kinds of flavours, IR UV red blue green, just pick one.
Not as cheap as a FT or KD one, but a lot better, and it has 2 modes so you are not obliged to toast the thing.
I own a SF with Sportac 1-mode drop-in for 5½yr now. It is recently promoted from EDC to nightstand light.
What led do they use?
Isn’t mentioned anywhere. But my experience with their CS dept. is very good. If they know, they will tell.
Believe it or not, I bought two of them when they were first released and were single-mode only.
Not sure, but I think they are now 2-mode....
@aL1, have you thought of asking them what kind of MCPCB, what kind of LED, and what kind of current they are running the LED at?
Never heard you mention the type of battery(s) you’re using. I have a few lights that if the battery discharges down to 3v they will just shut off.
^ That is a possibility.
First off I would take the Drop In out of the host and wire it directly to make sure it’s the Drop In itself and go from there—I’ve had ground issues athe the head and also around the switch
Should be the first thing to check, IMO. Battery and dirty contacts
They were not very helpful with any info.