I have had a marlin and a savage both in 22wmr do exactly what your describing. This may sound a bit odd but I noticed if I cycled the bolt lightly it would sometimes fail to fire, but if I cycled it with some authority it would fire every time. I would take a good look at your bolt and clean it very well especially the firing pin channel and give it a small amount of lube. Take it to the range and give it another try, see what happens. if all else fails, replace the firing pin and spring.