Same thing happens to both of my nitecore e-swtch lights: EA40 and HC50.
I put a new battery in, use it for 20 minutes and find the battery depleted in a month. Because my batteries are not protected, I got ~1V cells several times. I thought the cell was dead but according to the opus 2.2 they still retain good capacity, but I’m not very sure about them anymore. I’m concerned about the EC4S I just ordered, it might suffer the same problem.
Would like to hear if anyone can measure the standby draw of the S1.