SwiftUI & SwiftData: Fatal Error "Duplicate keys of type" Occurs on First Launch

Thread 1: Fatal error: Duplicate keys of type 'Bland' were found in a Dictionary.
This usually means either that the type violates Hashable's requirements, or that members of such a dictionary were mutated after insertion.

func refleshBlandsData() async throws {
    if let blandsOnServer = try await DataModel.shared.getBlands() {
        await MainActor.run {
            blandsOnServer.forEach { blandOnServer in
                if let blandOnLocal = blandList.first(where: { $0.code == blandOnServer.code }) {
                    blandOnLocal.update(serverBland: blandOnServer)
                } else {
                    modelContext.insert(blandOnServer.bland)
                }
            }
        }
    }
}

struct StockListView: View {
    @Environment(\.modelContext) private var modelContext
    @Query(sort: \Bland.sname) var blandList: [Bland]
    @Query var users: [User]
    @State private var isNotLoaded = true
    @State private var isLoading = false
    @State private var loadingErrorState = ""

    var body: some View {
        NavigationStack {
            List {
                ForEach(blandList, id: \.self) { bland in
                    NavigationLink(value: bland) {
                        Text(bland.sname)
                    }
                }
            }
            .navigationTitle("Stock List")
            .onAppear {
                doIfFirst()
            }
        }
    }

    // This function handles data loading when the app launches for the first time
    func doIfFirst() {
        if isNotLoaded {
            loadDataWithAnimationIfNotLoading()
            isNotLoaded = false
        }
    }

    // This function ensures data is loaded with an animation and avoids multiple triggers
    func loadDataWithAnimationIfNotLoading() {
        if !isLoading {
            isLoading = true
            Task {
                do {
                    try await loadData()
                } catch {
                    // Capture and store any errors during data loading
                    loadingErrorState = "Data load failed: \(error.localizedDescription)"
                }
                isLoading = false
            }
        }
    }

    // Fetch data from the server and insert it into the SwiftData model context
    func loadData() async throws {
        if let blandsOnServer = try await DataModel.shared.getBlands() {
            for bland in blandsOnServer {
                // Avoid inserting duplicate keys by checking for existing items in blandList
                if !blandList.contains(where: { $0.code == bland.code }) {
                    modelContext.insert(bland.bland)
                }
            }
        }
    }
}

@Model
class Bland: Identifiable {
    @Attribute(.unique) var code: String
    var sname: String
    @Relationship(deleteRule: .cascade, inverse: \CrossZansu.bland)
    var zansuList: [CrossZansu]
    @Relationship(deleteRule: .cascade, inverse: \Trade.bland)
    var trades: [Trade]
}

@Model
class CrossZansu: Equatable {
    @Attribute(.unique) var id: String
    var bland: Bland?
}

@Model
class Trade {
    @Relationship(deleteRule: .nullify)
    var user: User?
    var bland: Bland
}

class User {
    var id: UUID
    @Relationship(deleteRule: .cascade, inverse: \Trade.user)
    var trades: [Trade]
}