zNotes | lightweigh crossplatform application for notes management

I just performed a HeavyWeight core migration - im not sure where the line is between heavyweight and lightweight - this one involved 5 mappings and 1 custom class. I can certainly provide any of these. It seems to me that perhaps it may have been successful - my app is launching and it gets all the way to viewDidLoad - its only when it tries to do a fetchRequest that it crashes. I would appreciate any help debugging the following error message. I have some questions:

1. Did the migration work? Any way to know if it worked and if this is an issue with my fetch request or if somehow the data was corrupted or if it never worked at all. What is the best way to check this?
2. Why are there so many question marks in the SQL - does the mean that the migration is not working properly?
3. What is Z? all of the attributes seem to start with Z - "WHERE t0.ZNOTES IS NOT NULL for instance"
4. What is an NSSymbolicExpression? Where would it occur in the core data migration. I understand that somehow its trying to find the length of this object, and the object doesn't have that instance method. Does that mean it is assuming the migration is completed when it hasn't been for instance?

Information on any of the above would be greatly appreciated - including resources for where to find this/read more. I have been trying to learn about the migrations in apples documentation but am having trouble. Its been so trying... anything helps, thanks :)