When flying with an elytra at full speed chunks flicker behind the player and have more graphical issues than usual and the following errors are thrown in the log:

[22:27:57] [CullThread/INFO]: [STDERR]: 	at it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap$MapIterator.nextEntry(Int2ObjectOpenHashMap.java:674)
[22:27:57] [CullThread/INFO]: [STDERR]: 	at it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap$ValueIterator.next(Int2ObjectOpenHashMap.java:950)
[22:27:57] [CullThread/INFO]: [STDERR]: 	at dev.tr7zw.entityculling.CullTask.run(CullTask.java:92)
[22:27:57] [CullThread/INFO]: [STDERR]: 	at java.base/java.lang.Thread.run(Thread.java:834)

This was tested with EntityCulling-Fabric 1.1.0 and Fabric API 0.32.0 in Minecraft 1.16.5.

Chunks flickering/visual issues has (probably) nothing to do with this mod. This mod only may cancel block-/entity rendering when it happens, and can't influence chunk rendering/loading. The exception is expected and wasn't intended to be shown in the log.

Going to close this issue since it's most likely not related to this mod at all.