Tiny Worlds - Bug with unknown tiles on labs

[enricomir]

Describe the bug
Using Tiny Worlds, sometimes I got an unknown tile that is undiggable and undiscoverable.

To Reproduce
Steps to reproduce the behavior:
Load the savegame. On the right, above the AETN, there is such a tile.

I have digged around, moved everywhere around the tile but to no avail.

Expected behavior
The tile should have been explored when one of the rooms around was explored.

Radical Burrow.zip