Same problem, more than one tab open = freezing of settlers when go to different tab. I play several other flash games and this only happens on settlers.
Win 10 Home, 32 bit version
Chrome Version 59.0.3071.115 (Official Build) (32-bit)
Oddly, one work round seems to be to separate the chrome tabs by dragging them apart with one hiding the other. No idea why though.....
Incidentally, opening this thread to input the info above caused the game page to freeze, nuff said.