Navigation Bar black line with Large title - ios

Question

Thanks for taking the time to read.
Firstly, let me say that I have tried to do my due diligence in searching for a solution to the problem, but to no avail, and it is stressing me out! So, if someone finds an answer could you please point me in the direction :)
The problem I am facing is to do with the black line appearing underneath the Navigation Bar. Now, I am very much aware of the setting a default image/shadow image property of the navigation bar to correct this, and as such, I created my own extension to implement it (shown below)
func hideHairline(_ state:Bool) {
if state {
self.shadowImage = UIImage()
self.setBackgroundImage(UIImage(), for: .any, barMetrics: .default)
}else{
self.setBackgroundImage(UINavigationBar.appearance().backgroundImage(for: UIBarMetrics.default), for:UIBarMetrics.default)
self.shadowImage = nil
}
}
However, something seems to be misbehaving, and I am getting a black line appearing underneath my navigation bar (see below)
Whats more strange, is that the simulator does not show this line on the same screen. The simulator is set to be pixel accurate. (as shown below)
I think it may have something to do with the way I am changing from a previous VC. I am changing from having the navigation bar hidden, to shown, and it is set to prefersLargeTitles. Now, if I set the navigation bar, not to use the large titles, the black line doesn't show. Also, if I push to the next view controller, and then pop back, the line is not there (on the pushed controller, or the newly presented popped)
At this point, I am mainly just wondering why this is happening? I mean, I must have done something wrong. I wrote a setup extension, just to keep the code away from the VC, probably isn't the best coding practice, but hey!
self.hideHairline(true)
self.titleTextAttributes = [NSAttributedStringKey.foregroundColor : Constants.navigationBarTextColor]
self.largeTitleTextAttributes = self.titleTextAttributes
self.barTintColor = Constants.navigationBar
self.tintColor = Constants.navigationBarTint
self.isTranslucent = false
self.backgroundColor = Constants.navigationBar
self.prefersLargeTitles = true
The Constants is a class that holds all of the static variables in my app, such as colo(u)rs. Have I just made some stupid mistake, or is there a bug with large titles?
If you need any further information, please, just ask :)
Thanks

Answer 1

So, after taking a break for the evening, I have found a solution. I am going to leave this post up, for anyone else that might encounter a similar problem in the future.
It is to do with the view of the UINavigationController itself. I found another stack overflow post that answered it (link here)
All I had to do was:
self.navigationController?.view.backgroundColor = .white
change the colo(u)r to whatever you need it to be.
Simple solution, and I cannot believe it took me so long to figure out.
All the best.