When zooming out from a map to the point where the entire map is
visible, the bottom few tiles sometimes become invisible. They reappear
when zooming back in. Usually it's about two and a half rows of tiles that disappear. Similarly, if a map's background
image is larger than the map area, and the bottom part of the image is
not supposed to be shown because it's beyond the edge of the map
dimensions (for example, I have expanded a background image to cover an
area of 60x80, but then reduced the map dimension to only 60x40 so that
the players can only see the top half of the map), a few extra tiles
near the bottom of the map sometimes appear when zooming in to the map or
scrolling vertically. In other words, even though the map is only 40
tiles high, I can sometimes see tiles 41, 42, and part of tile 43,
including the background image and grid for those tiles. Scrolling the
map vertically up and down near the edge of the map makes the area that
shouldn't be shown appear and disappear. This doesn't
always happen, only on certain maps. I can't really find a pattern as
to when it does and doesn't happen. I am not sure if this is relevant,
but my Windows 10 display settings are set to have a scale of 125% for
all text, apps, and other items.