[Lizard]

Aha!
Adding a task to a project is a change to the project.
Changing a setting like "mark complete when completing last item" is also a change to the project.
It appears that we don't merge these two changes correctly.
After setting the 'mark complete' setting,
- sync the mac
- then sync the iOS device
Now it should be safe to add actions to the project, and the setting will persist properly.

Obviously, that's just a workaround, and we should look into fixing this.