This was my testing ground, they run top row, left to right 81 81 81, to 85 85 85, the second row, from left to right 86 86 86, to 90 90 90, with 140 140 140 on the bottom row. They are all 7x7 squares in map_heights, starting on an odd,odd tile and finishing on an odd,odd tile in map_heights.
At 84 84 84, the radar map was completely fine, at 85 85 85 however some black starts:
The radar map at 88 88 88, actual battle arena completely black.
The radar map at 90 90 90, i was expecting this to be completely black, but the left and bottom edges are the rapid decline of the square in map_heights. They were in the position of my first picture.