Footage of PTR: https://www.youtube.com/watch?v=e5sh4xMmWEw

• G29 does not have a Shuffling Horror. Maybe double check it but I really can't see it in the footage. That's the only thing I noticed was different.
  

This monster's patrol path goes out of the map, and it takes about 20-30 seconds before it suddenly teleports back.
This bug has been reported multiple times on the PTR, but Blizzard's designers probably haven't noticed it.

Ah, good catch. That explains why it isn't there then.