When using an end city portal it takes me to the wrong location. One time ended up in the void, another time it took me next to the exit portal. It seems to change every time I use an end city portal from an end city.

If I come in from the overworld and use it I get teleported to 5, 64, -2. Did more testing an ended up in a new location in a hole I dug. Not sure the reasoning.
If I use an end city gateway (at an island city) it takes me back to the main island then when I use the gateway that should take me back to the city it instead takes me to 0, 0, 0