You didnt't use version control when migrating to a new model. Before you make changes to your model you need to create a new version so that it knows to track the changes this way.
When I had this issue i tried many different soluyions (including renaming mom to momd and vice versa) and the only thing that worked was to start a new project. Same name, default core data. I built my model first, then i copied pasted all the classes, etc and then spent a few hours making sure it all connected and worked, etc...
Then I learned to use git, starting keeping version control, and started using model versions as well. Now if I run into a deadly error, I go back to the previous version on git and it's like nothing happened.
Good luck