Minions out of bounds during ritual

When I start a ritual altar and the map encroaches on me. When the minions end up in the black they can not re-enter the light side of the map and are stuck there until the ritual is done. Resulting in death most of the time.

Does not happen every time but more often on maps that have halways (not talking about doors, these are wonkey in a different way).
The minions can move normally trough the halway before the ritual but seem
stuck, like the way a door halway gets them stuck, when you start the ritual.