Thanks James.
So I did as you described and got some strange response from the RAM. I turned on Parallels and viewed iStat and Activity Monitor on the mac. It show the RAM usage jump from 6GB to 28GB when I open Parallels. So I go into task manager on Windows and surprising it said it was not sucking up much RAM.
In Mac’s activity monitor, it shows you a list of all applications that are taking up RAM and nothing much was there!!!???!!! I would calculate maybe 8GB yet 28GB is wired to something but I have no idea what. This only happens when turning on Parallels.
The best way I can describe the disappearing models is I will click off the viewport and sometimes, actually quite often, the model disappears for no reason. I then click back in the viewport, orbit around a little and up it pops again. It will also do this when modelling in the viewport sometimes when I click off the model into open space. I assumed it was a graphics card issue. I also used to get a lot of errors that I think were connected to the graphics card too but since upgrading, they seem to have gone. I am using Max 2017.
Thanks again for your response. I really appreciate it.