Well it’s up to you if you decide to believe an unnamed anonymous US source. Iran has denied the claim and it serves US interests for the claim to be believed.
The brilliant thing about the alleged malfunction of the Russian cruise is missiles is that apparently all 4 malfunctions by pure coincidence occurred over Iran, so the unnamed anonymous US source doesn’t have to provide any evidence at all.
If just one had malfunctioned over Iraq, which was also under the cruise missile flight path, then the unnamed anonymous US source might have been expected to perhaps provide some vague evidence.
So that was lucky then.
They spoke to a guy on R4 this morning who said there were (IIRC) four unaccounted missiles based on the number fired verses the number of known impact spots so the missing ones must have ended up somewhere.
I don’t see the problem though since missiles do malfunction. I think R4 guy said based on this usage the malfunction rate was about twice the rate of US cruise missiles which doesn’t seem terrible to me.