The understanding is that it isn't the missiles that are the problem but the guidance/tracking system. Since it was multiple of missiles of each type that failed.
This is the big confusion for me too
Standard Redut missiles used in other ships have no problems.
The standard Redut missiles are 2 variants of 9m96 40km & 120km plus 9m100 15km.Gorshkov
uses the same missiles as far as everything I've seen. (thats the point of a standardised VLS system)
Though maybe they (sensibly) never even considered trying the 120km version on 20380 -> it would be 'new' for Gorshkov
I thought that the 9m96 & 9m100 had been tested & gone into service as an integral part of S-400. (haven't actually seen any of those quad-packs showing on pics of actual service vehicles though)
I'd also got the impression they'd at least tested the S-350 which is the land analogue of Poliment-Redut?
20380 is said to have had issues with its Redut system because the Furke radar isn't strong enough (its a navalised version of the Pantsir radar), but it did eventually pass tests allowing them into service.
But when Gorshkov
with much more powerful radar has a similar issue of failed intercepts it kinda points to the missiles.
I ran into an older (& google translated) article which suggested 20380 only actually passed with a ~15km range interception using 9m100 guided by the Puma radar which would tend to point to the 9m96 missiles again.
Except 9m100 is an IR missile that probably doesn't require guidance & I've not seen any suggestion that the Puma gun firecontrol radar is capable of working with AA missiles so the credibility is low in my opinion
I also read an article talking about issues with Shtil-1 on the first Talwars
: apparently they had a similar issue of missile guidance failing, found the Puma was actually causing interference on the frequency used by the missile guidance, missile guys spent a bunch of time reworking things with insufficient improvement then eventually a senior radar troubleshooter guy sent over to India did something really basic like tweak the frequency of the Puma & quickly fixed it -> 2nd order from India.
Not sure how credible that is either.