Sorry for the late update, I wanted to monitor the behaviour before saying "Yay it's fixed" after only a couple of days.
So, it SEEMS to be fixed for now and I feel like I played myself. After the initial freezes I operated the RAM on XMP settings (so 3200MHz and 1.35V as stated on ....
Has your system remained stable? I am currently chasing the same gremlins on my z490-e system.