The issue is extremely minor, but there appears to be glitched chunks where light isn't rendered at all. Unfortunately, I haven't figured out how to recreate it, and I have experienced it only twice so far since 1.16.1's release.
Quitting then reloading seems to fix this issue.
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However, we are already tracking this issue, and this report is a Duplicate of MC-166508, which is a report that has not been resolved yet.
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