Something that got me in the beginning: the interaction between generators and autpilot:
The generators fail, when rotor RPM drops too low (this happens quite often when you pull collective too fast).
The autopilot also turns off completely when the generators fail (not just heading/alt hold, also the stabilizer channel. It makes the Mi-8 quite a bit harder to control)
Luckily, the generators come back online automatically when RPM is back to normal
The autopilot does however NOT come back on together with the generators. You need to manually push the button to get it back.
For this reason I always turn on one of the fans at startup. The fan stops spinning when the generators have failed and it resumes spinning when they are back. That way I know when I can re-enable the autopilot after a generator fail