I had same problem, in my situation was my gamepad fault, I don't know how the heck, but when after all tries I unplugged it, Sas returned to work properly. In previous version all worked fine exept sometimes Sas was going to bug, then I needed to restart all the game. In 1.8.1 I started to notice this problem when on the first check sat mission, it had a probe plus a Ch-j3 sas module, when I turn on Hibernation and left only sas module activate, all worked fine, instead the opposite setting (gamepad was always plugged in), In another mission with crew control plus the sas module, of course was not possible to change the situation. I tried too like in the previous version to reboot the game, but it not helped. In wait of a patch. At this moment , I just unplug the gamepad used only for aircraft missions.