It took me a while to find the reason but, lol, this is really unexpected one...
From the beginning... For some reason I could not see eco overlay, those that is togglable by F4. I asked about it many times but noone had the idea.
However I could see eco overlay while placing an eco building (mex, solar, etc): select a structure to build -> see overlay, that's how I was checking the grid for the long time :D
So now when reseted all settings and tried to tweak them again I found the reason.... Chili Minimap.... wtf lol? :D
If I disable Chili Minimap widget, F4 doesn't work. If I leave eco overlay enabled, disable Minimap, then eco is on always and I cannot disable it using F4 :D
Does F4 bound to **interface button***, those in Minimap window?! It sounds bewildering because my F1/2/3 work fine.
Guys, does anyone have the same behavior? Is it a bug?