Weak firing pin spring is my opinion.

The harder the primer cup the heavier the spring needed to guarantee they always go BANG.

Most Savage models have weaker firing pin springs than say Remington 700's. The strongest firing pin spring on any of my Savages is on a model 10 FCP-K (I can tell by the force it takes to re-cock the bolt not inside the action). This 10 FCP-K never had a FTF, and I can't say that about any other of my Short Action Savages. Also never had a problem with my Long action.

Also noticed the FTF's in my rifles have only happened in the very cold Canadian winter, with CCI primers. never a problem with Federal 210m primers.

My brother has a left hand mod 11 and it had a few FTF's. So I shimmed the firing pin spring(s) (it's a 2 spring design, I think the Axis is the same). And the FTF's went away.
Until last Saturday he had 1 FTF.
It was about -15 f with the wind and I thought the shell holder I used to sit the primers on the hand priming tool did not give me a positive bottom out feel (used a different shell holder than usual). So the jury is still out on that one, and the primer was a cci-BR-2.