I also have this same issue, but i have a Radeon R9 380.
My problem started when I updated to the Windows fall update (1709)
Weirdly I have two monitors, one HDMI and one VGA connected to my graphics card, only one cannot display 1920x1080.
I tried going through windows support but they only told me to update my drivers and said that not all graphics drivers are compatible with the fall update which again is rather stupid as one monitor displays 1920 x 1080 and the other doesn't.
If anyone can help us, this would be greatly appreciated.
As far as I know, this happened overnight (yesterday). There was no upgrade of Windows 10.
I downloaded the very latest driver (version 17.11.2 Crimson ReLive), but that didn't solve the problem.
I have contacted AMD technical support on this matter.
They have been very nice and helpful. But, unfortunately, they haven't been able to solve this specific problem.
Apparently, there is a conflict between the latest versions of Windows and the latest versions of the AMD drivers. Nobody seems to know why.
I'll keep you posted.