If I just run E along the edge of miners closest to the outside of the corner I also get this behaviour.
This also works if the belt turning into the row of miners is coming from the north instead of south, then it's just flipped.
I have not been able to reproduce it in singleplayer, with normal belts or with assemblers instead of miners.
First image is running NE along the miners
![Image](https://forums.factorio.com/images/ext/5b9ff70c5bff4ef07c63cbfac8e021d1.jpg)
Second image is the invisible box the player is trapped in
![Image](https://forums.factorio.com/images/ext/bbce4325483b6b3bb25215ee14d29a85.jpg)