Guild Wars 2

After you beat the boss and the cut scene plays, it WILL teleport you into the wall. This happened twice, the third time I got lucky and managed to jump out of the wall via a dangling vine.

Here is a screen shot, as you can see I managed to climb atop the wall from the invisible walls that trapped me.

For anyone else getting stuck here:

You can type /stuck in the chat window and wait for 30-60 seconds and it will teleport you to the beginning of the instance.

The command gives no feedback so be patient and don’t move or you will cancel it.