Can you file a feedback report with both models, and ideally, stores?

This issue should be resolved on the latest betas. Please file a feedback report if it is not.

The answer to your question is present in the error: "Validation error missing attribute values on mandatory destination attribute." You've previously saved some models with a prior version of a Schema that did not have the isApero attribute and in the latest version of the model, you've added that attribute as non-optional. You should check out [VersionedSchema] (https://developer.apple.com/documentation/swiftdata/versionedschema) and SchemaMigrationPlan