Thanks for the report! I have a version of this bug filed on Asana. I was able to reproduce space bar cycling humans, but so far I haven't had the next human button get stuck on me. I'll do some further testing and report back on this!
That's basically what happens (the cycling) i just thought that would be what could be happening (the button getting stuck), so when you press space it "clicks" it.
If you do not want to have to go all the way to the main menu i've found that clicking escape then going into the settings menu fixes it. Also alt+tab will fix it. Very strange and interesting bug.
