are you running multiple displays?
maybe Windows is being too aggressive with 'fullscreen optimizations"
UnrealEditor.exe->right click → Properties → Compatibility → “disable fullscreen optimizations”
is your GPU driver up to date {sometimes Windows tries to “help” and gives you an older GPU driver)
if your display has G-Sync/Freesync enabled then in might be competing with the engines default of VSync
- in the Editor: Edit → Editor Preferences → General → Performance → Editor Performance → Enable VSync.
check your “Power Plan” (even if this is a desktop) and CPU parking
- Window key → search “Power plan” → “choose a power plan” try either “High Performance” or “AMD Ryzen Balanced”
is discord “in game overlay” enabled?
Discord: Settings → Overlay → Disable In Game Overlay
AMD driver overlay?
does “New Editor Window (PIE)” make it better
from the level viewport there is the 3-vertical-dots menu on the same line as the Play button select "New Editor Window (PIE)
- you can kind of try this out by opening a blueprint, and clicking the play button from there.
could your GPU or CPU be overheating??
GPU reports tempt to task manager, but CPU might require like HWInfo64 or MSI Afterburner
try to manually lock values in the editor:
in the console for the Editor either with PIE running or not
“r.vsync 0” “t.maxfps 60”
these respectively disable VSync and set max FPS to the value given.
there is also “r.ScreenPercentage 100” but this is more for cooked applications.
you can also set Unreal Insights targeted to profile the editor itself, but this can have a lot of background noise in the capture.