Modelling dependencies

I'm stuck at an error EXC_BREAKPOINT (code=1, subcode=0x1a8d69a38)that is thrown in a class during initialization.

The class is defined as:

@Model
public final class Parent {

	@Attribute(.unique)
	public var uuid: UUID

	/// The date specification.
	@Relationship(.cascade)
	public var dateSpec: DateSpec

	/// The title.
	public var title: Title

	/// The subtitle.
	public var subTitle: Subtitle

	public init(uuid: UUID,
				dateSpec: DateSpec,
				title: Title,
				subTitle: Subtitle) {

		self.uuid = uuid
		self.dateSpec = dateSpec
		self.title = title
		self.subTitle = subTitle
	}
}

The error is thrown in the var dateSpec property at the return self.getValue(for: \.dateSpec) call of the @PersistedProperty macro.

DateSpec is defined this way:

@Model
public final class DateSpec {

	@Attribute(.unique)
	public var uuid: UUID

	/// The type of the date specification (`.point` or  `.range`).
	public var type: DateSpecType

	@Relationship(.cascade)
	public var point: DatePoint

	@Relationship(.cascade)
	public var range: DateRange

	public init(uuid: UUID,
				type: DateSpecType = .none,
				point: DatePoint = .init(),
				range: DateRange = .init()) {

		self.uuid = uuid
		self.type = type
		self.point = point
		self.range = range
	}
}

And DatePoint is defined so:

@Model
public final class DatePoint {

	@Attribute(.unique)
	public var uuid: UUID

	public var format: String
	public var date: Date?

	public init(uuid: UUID,
				format: String,
				date: Date? = nil) {
		
		self.uuid = uuid
		self.format = format
		self.date = date
	}
}

(DateRange accordingly).

So, as far as I understood the sessions, this should work. Or did I miss something?

-- Edit:

When taking out DatePoint and DateRange from the model, and replacing the properties by .transient wrappers that get/set the respective properties directly in DateSpec, then the error disappears.

So, is the problem the cascading of the relationships between Parent and DateSpec, and DateSpec and DatePoint/DateRange?