My Glock 40 came with a Vortex Venom RDS that would not hold zero. I replaced it with a Trijicon RM07 w/ waterproofing kit and that sighted in well and held zero, but would cut in and out at times. I shimmed the battery with a piece or the battery packaging and it has been 100% ever since. I put the Vortex venom on one of my AR's and it has held zero fine on that. Evidently the Vortex did not like the slide reciprocating.