well.. wish i had 14900ks.. so i could test it for you..
but the stability issue, still sounds very much like a combination of bad luck in the silicone lottery, mainboard not able, ram not capable.. you never mentioned what mainboard and ram you try to do this on.
i think most won't run dedicated tasks on specific threads, or have professional cpu's like threadripper pro or xeon handling tasks like those. The rest are all just gaming