I get this error even with explicitly setting the relationship in my class. I have a workout class and an exercise class. workout is composed of an array of exercises:

@Model
class Workout: Identifiable {
    var id: UUID
    var name: String
    var difficulty: Int
    var workingTime: Int
    var recoveryTime: Int
    var count: Int
    var duration: Int
    var isSet: Bool
    var setNumber: Int?
    var restTime: Int?
    
    // Define a one-to-many relationship with Exercise
    @Relationship(deleteRule: .cascade, inverse: Exercise.workout) var exercises: [Exercise] = [Exercise]()
    
    init(name: String, difficulty: Int, workingTime: Int, recoveryTime: Int, isSet: Bool, duration: Int, setNumber: Int? = nil, restTime: Int? = nil) {
        self.id = UUID()
        self.name = name
        self.difficulty = difficulty
        self.count = 0
        self.duration = duration
        self.workingTime = workingTime
        self.recoveryTime = recoveryTime
        self.isSet = isSet
        self.setNumber = setNumber
        self.restTime = restTime
    }
}

@Model
class Exercise: Identifiable {
    var id: UUID
    var name: String
    var imageName: String
    var difficulty: Int
    var guidelines: String
    var muscle: String
    
    // Define the relationship back to Workout
    var workout: Workout?

    init(name: String, imageName: String, difficulty: Int, guidelines: String, muscle: String, workout: Workout? = nil) {
        self.id = UUID()
        self.name = name
        self.imageName = imageName
        self.difficulty = difficulty
        self.guidelines = guidelines
        self.muscle = muscle
        self.workout = workout
    }
}

the error trigger when the user press the “save workout button”, defined like this, where exercises is an exercise array and workout a workout object:

private func saveWorkout() {
        modelContext.insert(workout)
        
        for exercise in exercises {
            exercise.workout = workout
            
            if var exerciseList = workout.exercises {
                exerciseList.append(exercise)
                workout.exercises = exerciseList
            } else {
                workout.exercises = [exercise]
            }
            
            modelContext.insert(exercise)
        }
        
        presentationMode.wrappedValue.dismiss()
        showModal = false
    }

I tried changing relationship parameters, allowing optionals exercise array, modifying order of the saveWorkout function, and changing my iOS target from 18 to 17.