No matter what I am doing in FGU (same for many extensions and for only Better Menus loaded), there is a brief hiccup every 10 seconds or so where FGU doesn't process any inputs during that ~1/3 second window. It is shown by the dips in 3D processing here:
https://i.imgur.com/QbbGJWF.png
This leads to clicking on unintended things when FGU processes clicks made during the lag where ever the cursor is after the lag spike.
Just toggling from Menu to Sidebar in Options with the extension loaded does fix the problem as well not loading the extension in the first place:
https://i.imgur.com/hDjJR4b.png