FYI: Looks like it’s still happening. It’s only when you set settings.conf to use only one monitor but you have two connected. If you allow retrofe to use both monitors, even without a layout for the 2nd it works fine. I’ve only learnt of it now as I’ve just started using 2 monitors as I like to keep one up for browsing, but have my main monitor running retrofe.
See my post above, if you want to continue using the second monitor outside of RetroFE then set "screenNum1 = 1" to be a value higher than your max screens (something like "screenNum1 = 2" would send the output to a non-existent screen (0 is screen 1, 1 is screen 2 etc)). You can have higher than connected but not lower.
numscreens is for physical screens connected, not for how many screens you want to use.
May work, may not.