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My best guess would be that, as you predicted, reflector made short circuit and damaged driver. One thing you can try is to disassemble everything, take the driver out, led, connect those two on a bench and test if you will get normal behaviour, if not, drivers is fried, sorry…
It sounds like a problem with the tail-cap is the light grounded properly? Maybe take apart the tail cap and see if it is soldered okay. Or that it is sitting right.
Unfortunately L2 weakest spot is the “reflector contacting the emitters solder spots ” issue .
Since i use fed dd drivers with 180 amp fets those can survive 3-4 burst shorts quite okay but i am usualy very careful, always before fully assembling it i do the “tail wire burst test”
Try as you may…but threads started LIVE, only to be deleted by the Gods. 