Hi,
I am not fully sure which model it is that you have tried to import, my guess is that it is the updated model that I attached to bug 482919. When I tried importing it in the latest build of Papyrus-RT (0.8.0.201701300526), based on the latest build of Papyrus (2.0.2.201701290246), and open the state-machine diagram in Capsule1, it opens up fine without exceptions. It looks like this
This pretty similar to you screen-shot so I guess I have tried the same model as you have. As you can see, no stereotypes shown as expected. The labels on the transitions are indeed missing though, including some aspects with the what I guess is the region. What also can be seen is that the diagram "goes bananas" if you try to resize the state-machine frame, and the "region" inside it (the colorued part), only becomes a tiny little square in the upper left corner, impossible to resize and you cannot even see the states and transition any longer.
So yes, there are indeed multiple (severe) issues still to be resolved and more testing is needed, and writing bugs for these issues. But as I said, I have not had the time and it has been a bit pre-mature to test the import of state-machine diagrams.
But at least I am able to import without the exception you are seeing. I suggest that you try this in the tester setup using the latest nightly of both Papyrus-RT and Papyrus, instead of your development environment.
/Peter Cigéhn