There have been reported issues with the .40 S&W Glocks (G22, G23, and the G35) with various weapon lights. Some seem to work with the lights while others don't. This is a well documented issue on other forums. Some workarounds have been to of course, replace the OEM springs with after-market springs and to update the magazine followers to the current #8 followers.
Even after the above changes, the results have been mixed and not 100% successful. The only option that Glock recommends is to use their branded tactical light. Even those have reported issues.
The believed underlying cause of the issue is the changing of the frame flex during recoil. As I understand it, the Glock .40 relies upon a certain degree of flex in order for the gun the cycle properly. When a shooter introduces a frame mounted light/laser, the angle and degree of flex is altered to a point that it changes the frame geometry - causing a failure to feed. Does this geometry change accelerate or decelerate the slide, I don't know.