Switches are the bane of all dive lights, always have been but they are improving, they will never be 100% but can get close. It’s probably best if anytime you (collective you) dive where light is life critical you should have at least one twist head, as in no switch and no power level cycling electronics, light, the king that makes and breaks contact only. I have a few of these simple lights, I prefer a good switch type light for general use but in the critical area of use a simple, dead simple back up is important.