Did you ever find an answer anywhere? I have almost the same issue (I'm not changing a property but merely adding a new one to the database model) and I have been searching and searching for help. Did a couple of tutorials which seemed very straightforward but still having this problem. Documentation is pitiful. Having to rely on Swift community and it's hard finding someone who's had the same problem.

I would love to know if you've found an answer to this problem. I had the same issue and having been searching everywhere for an answer with no real luck.