Creating a world with both Lithostitched and BCLib installed gives the following crash:
https://mclo.gs/zFsjw70
https://mclo.gs/ixFmeGs

Adding a mod that depends on Lithostitched, in this case Stony Cliffs Are Cool, seems to give a different crash report:
crash-2024-07-12_09.50.19-client.txt

Removing Lithostitched and its dependents fixes the issue.

This appears to be an issue with WorldWeaver, I have forwarded the issue to them.

Fixed in the latest WorldWeaver release. Thank you!