On player transfer to The Erebus there have been confirmed reports of the player spawning on top of the bedrock roof. The portal air gap is being created below the player in the correct place - just the player location setting is derping and moving the player to the top of the world. I have looked at the code and nothing seems like it should do this as the portal height is constrained in the code correctly.
As a temporary 'fix' I am thinking of adding a player event that checks if the player is above the allowed world height, if so, it will move them to the correct portal spawn location. This is not a particularly nice way of solving the problem but may sort out the constant headache that has been caused by the issue.

added event... we'll see...