I noticed it in UE4.19 in 4th preview. Problem could be present even before…
Yeah, I notice it in the final 4.19 build.
I found the solution:
1.I disabled GSync in the nvidia control panel for the Unreal Editor
2.closed everything
3.restarted the computer
4.works 120fps smooth
I guess you can replicate the bug with enabling just GSync, but i want to nore i have 2 monitors connected.
One at 144hz 2k and one full hd at 60hz. so maybe this setup caused it.
Anyway, hope they will enable GSync in a later update because on older versions everything worked great.