Big FPS change when content browser on 2nd screen

So I have three monitors, two 4k 60hz ones, and a 1080p one.
the HD and one of the UHD ones are connected to one gpu (780Ti overclocked)
(780ti cant handle all three screens, and only has one dp port)
and the other UHD one is connected to an nvidia 730 untill I finally have the money to get two 1080ti’s.

my UE4 is always open on the main 780ti uhd monitor, but whenever I move one of my menu’s to the other uhd screen that is controlled by the 730, the fps drops to 60fps.
I am using this 2nd uhd screen as means to have all the menu’s open there, and have clean workspace on the other uhd screen. Due to it being forced to being 60fps when menu’s are open on the 730 UHD screen I am noticing quite some slowdown.

When he menu’s are open on the other HD screen that is controlled by the 780ti the fps reduction is not happening.

I assume that this must be a bug, because ue4 is running trough the 780TI, its only some of its menu’s that are passed along to the 730, and imho that should not halve my fps.

Great to see this got an answer. Having similar problem and makes Unreal unusable.
Only 2 monitors. Content Browser on 2nd screen and fps is 15.

In my case it was because the 730 was anything but really up to the task to run ue4 properly.
When I changed the 730 for a low end 1030 the fps drop was gone because a 1030 can handle it quite a lot better.

Now I run one 1080ti on three monitors and its running fine on all three.

Interesting. I use a 1080, 8g vram.
Have had UE4 on this PC for over a year with no problems. Now suddenly out of nowhere I have this issue.

Actually, got drivers for new CoD, will rollback and see.