Caused by going near villages or spawning villagers.
Newest versions of Forge and Iceberg and tested without any other mods.

crash-2022-05-19_22.53.29-client.txt

Thank you for reporting this, would you happen to still have the latest.log file that was generated for this run? It contains a lot more contextual information than the crash log.

Actually I've just discovered the cause of the crash. I erroneously set the minimum forge version required as 40.1.0, which is what you are using, but it should be 40.1.6. I will release an update shortly that adds this requirement.

Iceberg version 1.0.42 is now available on CurseForge, which fixes this. (1.0.41 is archived now)
Enjoy! 😄