Periodic frame rate fluctuations in both GLES2 and GLES3

[snougo]

Godot version:

3.2.4 beta3

OS/device including version:

Issue description:

periodic frame rate fluctuations(higher than 60fps even Vsync is turn on) even in empty scene, in both GLES2 and GLES3, usually it's not big problem but in some case I will get like 100fps then back to 60fps, this is really bad

also I found already has a similar issue had been reported #38192

Steps to reproduce:
creat a spatial node
save this scene
run it
watch the fps in monitors

Minimal reproduction project:

issue.zip

[gianmichelemariani]

Do you have the same if the editor behind is minimized? I found myself on the same mac as yours (Catalina osx) that taking the editor out of the equation helps a lot.

[Calinou]

Duplicate of #16766 and possibly other issues.