When you are standing in very dark place, surrounded by blocks, and try to look up, you will see many pixels of sky in random places. Same pixels always appear in same aim position.
I remember the same issue in older versions of minecraft too.
Linked issues
duplicates 1
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Comments 5
Actually this is a mild appearance of MC-1794.
Please force a crash by pressing
F3 + C
for 10 seconds while in-game and attach the crash report (minecraft/crash-reports/crash-<DATE>-client.txt) here.