I finished studying the individual NPCR characters of the first 9 chapters. I added chapter 10 to the list and then hit the Study button, but no words were added. I then tried "Change study settings" and "Add vocab from" and to my horror found out that while the words were added 0% of the list was learned. So I did another "Add vocab from" and selected ". Then it showed 271 characters and 0% learned. At that point I was worried that not only my progress of the past month had been lost but also that all of my stories might have been deleted. I opened Progress and the graph still showed that I had learned 217 characters. I clicked on Study and strangely enough one of the last characters I had studied yesterday was shown. I went back to the list editor and all of a sudden it showed 85.2% complete and chapter 10's 40 characters left.
Perhaps the addition of characters to finished lists can be made a little bit less heart attack inducing?