Help needed on new build

Hi all

Having some problems with my new PC build.
It’s an i9 9900X @ 4.3Ghz / ASUS X299 Prime Deluxe II / 128G DDR4 2666 / M2 NVME Boot Drive

I’m using 2 Nvidia GT 710 Passive graphics cards, driving 4 monitors, 2 each - latest driver [25.21.14.2531]

Nuendo 8.3.20 installed - getting dropouts, and Audio Performance meter peaking…

I’ve run LatencyMon, which is showing Highest reported ISR time of 524 microseconds for dxgkrnl.sys
and Highest reported DPC time of 705 microseconds for nvlddmkm.sys

These are pointing me towards the Graphic cards…

Soundcard is RME MADI PCIe into SSL ALpha Link AX
[Haven’t changed signature to new machine yet!]

Anyone able to enlighten me?
Thanks
Andy