ASCII monsters dissappears - moving window across screens

[Canderel]

I have a super weird bug to report... I have 2 screens. And I've now moved my windowed game from one screen to the other, and the @ sign dissappeared, though the tactical view is still there. Also non-graphical monsters (rats and the like) also invisible.
But if I move it back (onto the screen where the game started) it's visible again.

btw... I am not blinded, I fired flare at the fox and the rat got blinded in the crossfire...