When I tested the new purge system, I had one set of foundation blocks, one door frame, NO DOOR, no placeables in a flat area of the open desert near the King Scorpion just south of Tower of the Bats. While most purges ran as they should, several claimed that the purge could not reach it.

There is an under-lying issue in the game.

EDIT - Stairs lead directly to foundation block with open door frame.

Single 5 x 5 room.

No jumping/climbing required to get to the doorway.

No defenses/barriers inside or outside.