Seems to be a regression that was introduced in Sodium 0.5.0-beta3. Some users reported that they were getting sporadic crashes in chunk meshing threads, which looked as if the WorldSlice was being modified while in use by other threads. Most likely, the changes to ClonedSectionCache are resulting in an issue where cloned sections can be re-purposed for new build tasks even when other tasks are still using it.

Fixed with a3111c1.