I'm not sure I agree about the "not easily reproducible" part. I have the problem with same chunks over and over 100% of the time (see light sources aren't working across entire chunk, destroy them all and replace, now they work, unload the chunk, reload the chunk, every light source in the same chunk has again stopped working), so filling a terrain with any light source and looking for the black spots ought to work on any seed. Mojang knew about it pre-release, and they knew about it after 1.14 came out, so I was surprised 1.14.1 didn't fix it since lighting is a fundamental aspect of the game. I appreciate and admire the technical skill it takes to track this stuff down, but it's a little hard to understand how the error can survive two intense development cycles.
I'm not sure I agree about the "not easily reproducible" part. I have the problem with same chunks over and over 100% of the time (see light sources aren't working across entire chunk, destroy them all and replace, now they work, unload the chunk, reload the chunk, every light source in the same chunk has again stopped working), so filling a terrain with any light source and looking for the black spots ought to work on any seed. Mojang knew about it pre-release, and they knew about it after 1.14 came out, so I was surprised 1.14.1 didn't fix it since lighting is a fundamental aspect of the game. I appreciate and admire the technical skill it takes to track this stuff down, but it's a little hard to understand how the error can survive two intense development cycles.