@Skywalker OG : That totally sucks for you, what a shitty situation to be in.
But I can say this about 2 authentic Nitecore chargers I use and tested.
Neither unit charges to the proper voltage.
Both take all 18650 batteries to 4.20V at full charge, but when testing the fully charged batteries with multiple mutimeters they show the Nitcores don't bring the batteries to the proper voltage. They come out of the charger at 4.14V - 4.15V.
If anyone has a multimeter and a Nitcore try charging a Grasshopper battery in it and charge one in the Grasshopper with usb and compare the fully charged voltages.