[Raigen.Convict]

As Pictured here, it's possible to place pawns inside of certain solid map objects.

Replication method: Select Form Pawns, place the '1' square inside of the solid object, then place the '2' square on a normally valid tile. 
I have not done extensive testing of this but I can only assume if this works on this object, it'll work on a number of others.

[Neus]

This has been corrected in 2.82 v3.