Why has my .308 stalking rifle started to misfire?
Since you were using factory ammunition, I would confidently rule this out as the cause of your problems, as this type of ammunition is so well made these days.
It would only be suspect if it was very old or had degraded due to the presence of moisture.
If, however, you had been using reloaded ammunition, then there is a possibility that you might have been having a problem with primers.
I think it is far more likely that your ignition system — i.e. the bolt spring, striker/firing pin — is causing the light strikes.
Firing pins are usually well hardened to take the repeated firing and contact with the primer to initiate the ignition process, but over time they can become damaged by loose brass filings, fouling or harsh use, so that the end of the pin can be reduced in length, thus not reaching as far forward as usual.
In addition, the spring that tensions the firing pin will weaken over time so that the primer may not be struck as forcefully as it should be.
I would remove the bolt and check out these points, or take it to a reliable gunsmith to be checked.
The problem could, of course, be something simple, such as solidified grease in the bolt.
In winter, the grease used to lubricate the bolt firing mechanism can become more viscous and thus slow down the speed at which the firing pin strikes the primer, so causing a misfire.
Remove the grease and replace it with a lighter grease or moly slide lubricant.