Nevermind, I found the error. It appears there was an old FSM sitting in the resources folder that was referencing nodes that no longer existed. Updating Nodecanvas must have forced the old FSM to refresh its references which might explain why the error was not appearing in the previous version.
Thanks for letting me know you’ve found the guilty graph. 🙂
This error indeed appears to inform you if a class “referenced” by NodeCanvas somewhere, could not be resolved, meaning that it has either been deleted or renamed.