map wall colors wonky

My map walls have jack-o-lanterns for backlighting.

Depending on the angle that I'm looking at the wall, some of the maps will appear dark.  I have four walls (zoom 0,1,2,3) and all four have exhibited this behavior.
I can move around and find a spot that will show the maps perfect and move one pixel to get dark maps.
It used to fail sometimes, and would choose different maps for dimness each time I joined. But the last several days this wall has been consistently this pattern of maps that are dim.