Thanks for the rec!
Re: Screeching Cobra, my intent was to have the cobra provide an obstacle to the party escaping through this way, but I can see how it could feel really sudden and wake Satur without any player choice.
A possible remedy could be that the screams from the Cobra starts off softly and gets louder with each moment in the room, giving the Party enough time to go back but not enough time to get to R3.
I will try and amend this when I have time.
Thanks again!