When traveling through the nether, light sources seem to break. I pick up the torches or lanterns, put them back down and it's fine. Then I make a trip to the Nether, and when I come back, it's broken again. Mobs spawn there, and it says light level 0.

Tried reloading chunks and optimize world, nothing works. Didn't have this problem in 1.13.2, so it has to be a 1.14 bug. I've had it both in 1.14 and 1.14.1 (pre-release).