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

Second image is the invisible box the player is trapped in
