Awesome, thank you very much @petrus.hyvonen ! Orekit community support is impressive as always.
I should have insisted more on the Python side of things, since I clearly struggled to put together the subclassing. I had played a bit with the init method and the of_ method as I suspected an issue with the Java generic types. But since the symptom was so similar to issue #663 I jumped to a bad conclusion. I made a false bug accusation, for which I must apologize sincerely !
What would you think of putting the updated example into the Python Wrapper documentation ? I noticed that the basic tutorial has no code sample for interface subclassing. This example is maybe a bit more complex, but I think it is a fairly common use case to implement a maneuver at a certain position angle. I can make the change if you agree.
Binder is indeed very well put together. Maybe we could consider offering the Python Orekit tutorials on it as well ? The main drawback is that, as far as I know, it works only with github repositories.
Thanks again.