Hi there and sorry to here,usual contacts cleaned and all spotless threads i presume just to rule out.
After that,its a large light so left on or not it is faulty,after seeing some pics of the internals its far from over kill regarding any heat dissipating measures. I would be contacting nitecore,mentioning this thread and mention many also interested in outcome. If nothing back(may have a holiday over in China.........dont know but its always something to bare in mind) allow 24-48hrs and send again. It took me a week with fenix,similar issue but small light ,just worked at 1st then flickered to nothing..........I am not one for backing down out of principle so my emails got more to the point with more harsh but polite wording. Once i got a mail back all was good and contact was good,just the 1st mail(same with klarus too).
Just to add the above is if bought from China or an over seas retailer. If local hopefully the outcome will be a lot quicker/easier. Thats one issue with ordering from over seas,its always a pita and could involve sending light off for weeks/months in total...................no matter if nitecore or fenix or .............(thats a presumption as i dont know where purchased)
Sure other advise on its way,i can only say what i would do and have done,good luck,if it does come to contacting nitecore dont back down and i hope what ever the outcome its as swift and professional as it can be.
Regards ven