Hi Karsten,

re:
> the problem was that the network factory need curves that are already added to the
> database - otherwise the factory shows this in the crash report:

I'm glad you found the problem! This issue of not being able to use "loose" objects that are not in the database with an async factory should be solved in v4. The problem was that previously a newly created object was not assigned a unique id value until it was added to the geometry database, while in v4 this happens right when objects are created.

- Michael