Sunlight passes through blocks placed near sea-level

Blocks placed above sea level (around y = 63 to around y = 80) aren't blocking out sunlight like they should - block levels closer to y = 63 have brighter sunlight, and as you go up the light level lessens until it's at the proper level.

(I discovered this on day 3 of constructing a tower-style mob farm, and the bug renders the lower half of it nonfunctional)