resolution restricted after dnf update

[Gary Stainburn]

I have a dual headed F23 system using a NVidia graphics card.  Everything was 
working fine until today when I installed the latest set of updates.

Both screens were set to 1280x1024 resolution.

However, since I rebooted after completing the update, my right hand side 
screen is now limited to 1024/768.

If I look in System Settings -> Display Configuration it correctly recognises 
my left screen as a CY765. However, the model of my right screen is no longer 
recognised, and just shows it as VGA-1 which is it's port.

I'm certain that it used to know the model of that screen too.

Can anyone suggest how I can get this resolved, or at least where to look to 
find the problem?

Cheers

Gary