Some times when walking I get an odd glitch, where a different part of the map appears the the row of squares that just left my screen. It also appears like that on my mini map, until I re-explore it.
i got something similar quite often.
only, when i go northwards.
then on the right side of the screen the bordertiles show parts of buildings, or landscape tiles, that obviously don't belong there.
Most often is going into TB's southeastern gate. When I get to a certain point, the edge tiles at the right will change to anything from rocks to desert to even forest ground... Or buildings, where the river should be.