Create a notebook using some link. Say https://github.com/gudnm/codekatas/blob/master/codekatas.ipynb
put a break point and start debugging. press n a few times to debug a few lines. Then hit stop. Notebook gets into an irrecoverable state. Does not stop debugging. Cannot resume debugging. Go back to project, it no longer lists the notebook as running. Wait for 15-20 mins. Go back to dashboard and the project. Now you may see the notebook there if you are lucky. You will that kernel is still running if you click on right menu for the notebook. Stop kernel and then you will be able to debug it. Not sure if its Jupyter thing or IBM but its very inefficient and does not let you code.