This error indicates that your model object doesn't have a valid model context, which can happen when you hold a SwiftData model object in a SwiftUI view and continue to access the object (as the view is updated) after it was deleted. In my case it was exactly as @DTS Engineer pointed out. One of my parent views State properties was holding a model object where the relationship property was a deleted model object. That relationship was still accessed in the parent view and lead to the crash. Explicitly setting those states to nil helped resolving the issue. It took some time to identify where the issue happened exactly. What helped was the backtrace of the main thread inside the Debug Navigator. Hope that helps.