hello and thank you for replying.
Kevin, the server is using a intel rst raid at bios level, so a sort of software raid.
continuum, the client is the same server 2019. just in #1 im on the server desktop itself copying the file to a share setup on the win 10 machine. in #2 I was copying the file from the servers share using the win 10 desktop.
its all very odd as the issue seems to go away if I use the Kingston 2400mghz memory as opposed to the Corsair LPX 3000mghz stuff.