So I had 3 hours on Cubase last night without a single crash 
So happy! To test it properly i left 10 tracks of VST and audio and FX playing in a loop overnight. Problem solved i have a stable Cubase!
Solution - I completely uninstalled the AMD Ryzen driver for the graphics adaptor. So the graphic driver is now the generic windows driver. I suspect i’ve lost my super smooth graphics ability (should this be reported to Steinberg or AMD?) but i’ve gained the primary reason for the PC.