Using a modpack: All the Mods 6 - 1.7.4
It has the following IE, and dependents:
ImmersiveEngineering-1.16.5-5.0.2-137.jar
ImmersivePetroleum-1.16.5-3.3.0-5.jar
immersiveposts-1.16.5-4.1.1.jar

Description of the issue:

Extreme log spam on client when Coke Oven is running. Unsure of later blocks as I haven't progressed quite that far yet.
After a good amount of errors go by, they get truncated to:
[Render thread/FATAL] [minecraft/ThreadTaskExecutor]: Error executing task on Client
and occur about 3-4 times a second.

Crashlog:

Doesn't cause a full crash, but has consumed over 15MB in about 30 minutes, almost entirely from this log spam.
https://gist.github.com/Sakata-MC/22c8109165cd9724955888fa174691a2

Versions & Modlist

AtM6 1.7.4:

Minecraft 1.16.5
Forge 36.2.0
Immersive Engineering 1.16.5-5.0.2-137

Are you sure the mods on your client exactly match the ones on the server? From the code it looks like this might happen when a mod has slightly different block definitions on the server than on the client. I haven't seen this happen to anyone else, so it's probably something about your setup.

We seem to be getting a similar issue with a Coke Oven and a Blast Furnace producing a render issue.

https://gist.github.com/InsaneJ/b6147dc7e81d21fc679f7d96f0a9403a

I've verified that both server and client are running:
ImmersiveEngineering-1.16.5-5.0.5-140.jar
Forge 36.2.9