I try to add new item in array who already fill from an API, but i got an error when my item finish displaying in my onboarding. this is my error

“*** __boundsFail: index 3 beyond bounds [0 .. 2]”

i know the problem is, but i still can’t fix it. The problem is since i mixed a hardcoded data with the data from an API i populate the data wrongly.

this is my viewModel

enum FilterKey {
    static let regular = "regular"
    static let hajj = "multicasa_hajj"
}

class OnboardingViewModel {

    var thematicItems: [ThematicItem] = []

    func getThematicItem() {
        getMulticasaConfigUseCase.getThematicItem()
            .subscribe(onSuccess: { [weak self] thematicItems in
                guard let strongSelf = self else { return }
                strongSelf.thematicItems = strongSelf.addNewThematicItems(items: thematicItems)
            }).disposed(by: disposedBag)
    }

    private func addNewThematicItems(items: [ThematicItem]) -> [ThematicItem] {
        var thematicItems = items
        
        thematicItems.append(ThematicItem(key: "regular", imgURL: "some https image url.png", title: "label_multicasa_onboarding_page_title_0".localized, description: "label_multicasa_onboarding_page_desc_0".localized, content: nil, visible: false, order: 1))
        
        thematicItems.append(ThematicItem(key: "regular", imgURL: "some https image url.png", title: "label_multicasa_onboarding_page_title_1".localized, description: "label_multicasa_onboarding_page_desc_1".localized, content: nil, visible: false, order: 2))
        
        thematicItems.append(ThematicItem(key: "regular", imgURL: "some https image url.png", title: "label_multicasa_onboarding_page_title_2".localized, description: "label_multicasa_onboarding_page_desc_2".localized, content: nil, visible: false, order: 3))
        
        return thematicItems
    }
}

This is my OnboardingViewController in viewDidLoad

class OnboardingViewController {

    viewModel.getThematicItem()
    let thematicItems = viewModel.thematicItems
        
        switch onboardingType {
        case .regular:
            let regularOnboarding = thematicItems.filter { $0.key == FilterKey.regular }
            pagingProgressView.pageSize = regularOnboarding.count
            
            regularOnboarding.forEach {
                let onboardingView: OnboardingPageView = .fromNib()
                onboardingView.setup(thematicItem: $0)
                
                stackView.addArrangedSubview(onboardingView)
                
                onboardingView.snp.makeConstraints { make in
                    make.size.equalTo(scrollView.snp.size)
                }
            }
        case .haji:
            let hajjOnboarding = thematicItems.filter { $0.key == FilterKey.hajj }
            pagingProgressView.pageSize = hajjOnboarding.count
            
            hajiOnboarding.forEach {
                let onboardingHajiView: OnboardingAlaHajj = .fromNib()
                onboardingHajjView.setup(thematicItem: $0)

                stackView.addArrangedSubview(onboardingHajjView)

                onboardingHajiView.snp.makeConstraints { make in
                    make.size.equalTo(scrollView.snp.size)
                }
            }
        }
}

How the correct way to populate the data so is not crashing?