As long as playing singleplayer the size of log files is normal. However, when joining any multiplayer server, client log files are being spammed with errors, making them several gigabites large within the span of a few hours. This happens on every server I tried to join.

The error:

[17:01:46] [Render thread/FATAL]: Error executing task on Client
java.lang.NullPointerException: null
at ddn.d(SourceFile:199) ~[1.16.5.jar:?]
at dwu.a(SourceFile:2156) ~[1.16.5.jar:?]
at ri.a(SourceFile:122) ~[1.16.5.jar:?]
at ri.a(SourceFile:16) ~[1.16.5.jar:?]
at ol.a(SourceFile:21) ~[1.16.5.jar:?]
at ol$$Lambda$3390/688149207.run(Unknown Source) ~[?:?]
at aob.c(SourceFile:144) [1.16.5.jar:?]
at aof.c(SourceFile:23) [1.16.5.jar:?]
at aob.y(SourceFile:118) [1.16.5.jar:?]
at aob.bl(SourceFile:103) [1.16.5.jar:?]
at djz.e(SourceFile:1015) [1.16.5.jar:?]
at djz.e(SourceFile:681) [1.16.5.jar:?]
at net.minecraft.client.main.Main.main(SourceFile:215) [1.16.5.jar:?]