I had one weird encounter on the map in the round room with the hole in the middle.
So basically, I was with my friend having fun, when we saw the room with no door showing only darkness.
As soon as I went to this darkness, the door appeared behind me also I started to hear demonic hissing and heavy breathing (it was louder than almost every ambient in this map.
I probably have missed this encounter 'cause I got scared and flew away using noclip.

When I cleaned up and even reloaded the map, nothing like this did not happen.