Weird Editor Framerate

While UE4 Editor used to work fine for a couple of years, I now notice weird framerate issues.
The editor window runs at 37 FPS when focused.

  • It drops to 25 FPS if my mouse hover a button.
  • It raises to 45 FPS if Unreal is not focused at all (click on desktop).
  • It maxes out at 60 FPS (the value set in project settings) if any window of Unreal is focused,
    except for the editor.
  • Playing the game is inconsistent: sometimes it runs around 40-ish FPS, sometimes around 20 (while it used to run smooth at 90+ FPS).

That’s what puzzles me. If I uncap the FPS, the editor is capable of running at 180 FPS when I focus the content browser window, so it’s not a hardware issue. As soon as I click on the level editor, it drops dramatically.

On this screenshot, you can see how it drops to 25 FPS when hovering a button, even though no level has been loaded. (yes, it’s 25 FPS for a black screen).

Any idea? Maybe some settings went wrong?


I forgot to add.
Win10, UE4.22, Intel CPU (8700k), 2 screens on nVidia 1070 (drivers 425 and 430), 1 screen on iGPU, 32 GB ram,

Addendum: things are very inconsistent. Sometimes I get normal FPS, sometimes it’s slow. Today’s new discovery is as follow:

  • I put the main editor window (containing the level) on my main screen (2560x1440@75Hz) and I get 30~40 FPS.
  • I move that main window to my second screen (1920x1200@60Hz) which is on the same gpu, I get 60 FPS.