Precision Mobile Workstation 7670 Remote Desktop FAIL!

Hello all,

I have a brand new Dell Precision 7670 16 inch portable workstation with OLED 4k display that was built for me by Dell under warranty when my old Precision 7730 17.3 inch 4k display refused to charge any more (it suddenly complained one day that the power adaptor wasn't from Dell and after exhaustive testing by myself and Dell, concluded there was a motherboard fault - you can read all about this problem from other people on the Dell forums). 

The 7670 has a much smaller power supply and will also charge quite happily from the one that would not work with the 7730! 

But I now have another problem that has defeated me so far. I use the device quite often to Remote Desktop or Teamviewer Remote to my main PC elsewhere in the house which runs at 1920x1080px or 3840x2160 depending on what I am doing as my eyesight is not what it was.

It doesn't matter what I do and believe me I've tried everything over the past week that I could lookup/find/advanced options etc etc and it will not RD to my main machine at 1920x1080px or even full res at 3840x2160 but always ends up on the 7670 at 1024x768px in both RD and TV. The 7730 never had any trouble matching the remote resolution whatever it was set to so I saw a clone of the remote desktop. Now it always shows a desktop in a complete jumble from about half way down and on the right of the screen since there is insufficient resolution now to fit everything in where it was. 

https://www.wpocomms.co.uk/images/7670 Remote 1.jpg

The above photo of the TeamViewer desktop shows a very much reduced central area (actually 1024px worth of 3840px) and the Resolution dropdown shows it knows the remote screen is 3840x2160px but has selected 1024x768px. Selecting any other listed resolution has no effect. All the icons are the wrong size of course.

 With Remote Desktop I get a complete desktop view but jumbled up at 1024x768... It is still usable but not very helpful.. 

 I also installed and tried the MS Remote Desktop app but same result.

The only other thing I could try is to temporarily disable the built in Nvidia RTX A2000 graphics card and use the Intel UHD graphics. However, the latter is shown as needing further installation in Device Manager so  not sure what to do - I suspect RD uses.its own driver? I doubt there are many of these machines about yet.

 Just to check I powered up the 7730 still works as it should.

 If anyone has any ideas I'd be grateful as I'm tearing my hair out

 Tony