The reality remains, however, that unless the failure rate is frankly absurdly high (implausible so) that the damage wrought by Russian weapons would still be far more than any nation would be willing or, apart from perhaps the US, to bear. Quite apart from the effects of flattening Russia upon the global climate. The reality is that of course some weapons will fail. I have no doubts that that some NATO missiles and warheads would fail to operate properly. These are extremely complex weapon systems that, whilst they've been rigorously tested, are like any complex system and will suffer failures. But the rate of that failure is likely to be so low as to not really make a material difference. Some provincial city in darkest Siberia might be spared because it only had a single warhead targeted on it and that warhead was a dud. But it won't matter because hundreds of other warheads on other cities, infrastructure, military and political targets will have functioned flawlessly.
I really wouldn't get side tracked onto this line of thinking, there is no evidence to suggest that the entirety of Russia's strategic nuclear forces are unusable.