Surely the line indicated by the error message provides a hint, or at least a lead. From internet searches the best I can find is this: https://forums.unrealengine.com/t/pure-virtual-function-being-called-only-on-pac...
If I were to guess. Perhaps you have a UI widget referencing an object in the procedurally generated map, but the widget is loaded before the level is fully generated and thus it might try to fetch data which doesn't exist yet, but I have no experience debugging Unreal projects.