I have the same issue when only wanting to use 1 monitor. Reverting to 10.31 and using the settings.conf file and core folder from it, appear to fix the issue for me. Hard to tell as it's inconsistent, but so far so good. I do occasionally like to use 2 monitors, so I'll write a script, for now, to copy over my previous core folder and settings.conf file when wanting to use 2 monitors.