What happend to appState?

Yes or no.

Edit: you can learn more about why that’s important here: AppState interface usage poll

Essentially, if you implement AppState directly instead of extending AbstractAppState then you have to take responsibility for every interface change. getId() was added to the interface. If you extend AbstractAppState then you won’t have this issue in the future.

If the problem is really to do with BulletAppState then you are mixing libraries from different JME versions somehow.