I was playing with the Auntie Ethel encounter and found what seems to be a bug with using Stealth mode. After entering the Ancient Abode, I started crouching and moving between heavily obscured areas. The first time I tried it, the "Surprised" message did appear, but the hag did not. I was able to move down to the Control Globe and free Mayrina, but she behaved as though the hag was still active and would not move from the cage. I was then able to enter the workshop and loot all of the equipment. I restored and tried it again, but had one character stand up out of crouching. In that case the hag did appear. I was able to knock her into the abyss and Mayrina acted as if she was killed.
I also was unable to do anything with the addled frog even after killing the hag. What else is needed?