I remember a scandal around a decade ago where it turned out a singular wrench specific to minutemen warheads had to keep getting shipped between multiple different bases due to general degradation and mismanagement of US nuclear forces. It was enough of an embarrassment that it ultimately resulted in something like a $300 billion dollar refurbishment program for the whole triad over the next three decades.

So for the answer to that question, a lot of them didn't work... and now they do.

Can you provide details? I’ve not heard any concern about the readiness of US weapons, but have heard a lot since the Ukraine war about the poor state of Russian military equipment.