I’m not sure why that would be, but you should make sure inside shortcut to UE4Editor.exe flag is still set: “C:\Program Files\Epic Games\UE_4.16\Engine\Binaries\Win64\UE4Editor.exe” -enablehighdpi
And also make sure in compatibility tab that “Disable display scaling on high DPI settings” is NOT selected.
You will likely need to reset flag for each new engine update you do (ie. 4.15 to 4.16), but not for hotfixes (ie. 4.16.0 to 4.16.1). I hope that helps!
-Adam