Steps to reproduce:
Walk through the Gnomeregan pre-instance and into the Gnomeregan instance portal
Attempt to walk back out
Observe that you’ve now been transported to the Grom’gol Base Camp
I noticed this when I teleported from Dalaran to the pet dungeon NPC and then absent mindedly entered the instance… couldn’t get back out to the pre-instance to ask the NPC to start the pet battle dungeon.