Sometimes the lighting doesn't cast properly and areas are darkened until I update a block near them, I've seen this occur on several occasions, but attached is the most recent issue after the 1.16.1 update.

This issue occurred before the nether update.

I'm running a Ryzen 7 2700 with an RTX 2080 Ti

If I plant a torch nearby, the surrounding lighting is recalculated, but any shadowed areas outside the AoE of the torch do not appear to update