[β0.18.1722] Invisible pawn 'go to' blocks

[Chibiabos]

I've long noticed a quirky issue with giving drafted pawns 'go to' movement orders, in that for some reason, I can't order pawns to go to specific tiles despite there a) not being anything obstructive (like a tree) in that tile and b) no other pawn has been given movement orders to that tile (I do know only a single pawn can be given an order to go to a single tile).

I am currently playing with mods (Prepare Carefully, HugLib & Hospitality), but this is an issue I've seen in vanilla.  I have attached a screenshot showing which tile is currently seemingly inexplicably blocked; the green circle with checks I can order pawns to go to, but not the red circle with an 'X' immediately below the door.  Here is the savegame (again it has mods -- Prepare Carefully, HugsLib and Hospitality -- but I report with confidence I have seen this issue in vanilla games, its a bug I am not certain what triggers it, so I don't know how to recreate it to submit a clean vanilla occurrence):  https://drive.google.com/open?id=1kS7gkGCyycbXvDlLKtCxbtMZ-5a9L0gq

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[ison]

Fixed, thanks!