Has anyone run into this issue? XTAR D26 2500, works for about half an hour, then brightness drops, the switch starts flashing red, and a few minutes later, it dies. The batteries are original XTAR-branded 26650s that shipped with the light, and testing them in a smart charger shows approximately 4950mAh capacity. In fact, removing them from the light and popping them in the charger after it has died shows that they've barely been discharged at all.