I’m testing my app via TestFlight at the minute. Out of about 10,000 sessions, I have 6 crashes reported in sentry with the above title, when the app is backgrounded. Crash reports from TestFlight offer very little to go on:

Sentry offers a little bit more info, with the title/description of:

SIGABRT

Cannot form weak reference to instance (0x1055809f0) of class UIWindow. It is possible that this object was over-released, or is in the process of deallocation. > objc[6171]: Cannot form weak reference to instance (0x1055809f0) of class UIWindow. It is possible that this object was over-released, or is in the process of deallocation.

And breadcrumbs showing it happened after the app was backgrounded:

The only thing that I do consistently with the window when backgrounding is cover the screen with another window to protect users private info (financial data)

Inside SceneDelegate’s sceneDidEnterBackground I run this

func showPrivacyProtectionWindow() {
    guard let windowScene = self.window?.windowScene else {
        return
    }
        
    privacyProtectionWindowVisible = true
    privacyProtectionWindow = UIWindow(windowScene: windowScene)
    privacyProtectionWindow?.rootViewController = UIStoryboard(name: "Login", bundle: nil).instantiateInitialViewController() ?? UIViewController()
    privacyProtectionWindow?.windowLevel = .alert + 1
    privacyProtectionWindow?.makeKeyAndVisible()
}

This covers the screen in a company logo, and upon returning to the app, forces the user to enter a passcode. Once done its removed via:

func hidePrivacyProtectionWindow() {
    UIView.animate(withDuration: 0.3) { [weak self] in
        self?.privacyProtectionWindow?.alpha = 0
            
    } completion: { [weak self] finish in
        self?.privacyProtectionWindow = nil
        self?.privacyProtectionWindowVisible = false
        self?.dismissedPrivacyProtectionWindow = true
    }
}

This is the only thing I can think of that might be causing the issue. But it works 99.9999% of the time and I can’t reproduce the issue. Anyone have any idea/guidance on what might be causing this and how to address it?