Display of dialogs in the Unity editor corrupted on 4K Display

I have searched but have a problem with the unity editor I can't fix. The display of dialogs in the Unity editor is either not correct or is corrupted.

I am on Windows 10 with a Asus PB287Q 4K monitor (DP1.2 60Hz) and Unity 5.5.0f3 (although this is the same in 5.6 and 5.4). I have two 1070s in SLI mode (same with SLI mode off, haven't removed one card yet) with a Vive connected too.

The only thing that fixes it is to start Unity with -force-d3d9 but this then breaks VR and crashes Unity every time you run a project with VR.

Disable display scaling helps, but doesn't fix it, although the text is then pretty horrid to read.

This is the only app this occurs in. Just running the mouse over the dialog refreshes it so its useable, but its painful.