Problem in center an ActivityIndicatorView in a UIButton

I'm trying to center a UIActivityIndicatorView in a UIButton programmatically using constraints but it's not working.. Note: It's centered if you rotate the device!

The code i'm using is

func animateButton(shouldLoad: Bool, with message: String) {
    
    
    self.isUserInteractionEnabled = !shouldLoad
    
    // Should start loading
    if shouldLoad {

        self.setTitle("", for: .normal)
        
        UIView.animate(withDuration: 0.2, animations: { 
            self.layer.cornerRadius = self.frame.height / 2
            self.frame = CGRect(x: self.frame.midX - self.frame.height / 2, y: self.frame.origin.y, width: self.frame.height, height: self.frame.height)
        }, completion: { (done) in
            if done {
                self.showLoading()
                UIView.animate(withDuration: 0.2, animations: {
                    self.spinner.alpha = 1
                    self.layoutIfNeeded()
                })
            }
        })
        
    // Should end loading
    } else {
        
        self.setTitle(message, for: .normal)
        
        for subview in self.subviews {
            if subview == spinner {
                subview.removeFromSuperview()
            }
        }
        
        UIView.animate(withDuration: 0.2, animations: { 
            self.layer.cornerRadius = 5
            self.frame = self.originalFrame!
        })
        
    }
    
}

func showLoading() {
    if (spinner == nil) {
        spinner = createSpinner()
    }
    
    self.addSubview(spinner)
    centerActivityIndicatorInButton()
    spinner.startAnimating()
}

func hideLoading() {
    spinner.stopAnimating()
}

private func createSpinner() -> UIActivityIndicatorView {
    let activityIndicator = UIActivityIndicatorView()
    activityIndicator.activityIndicatorViewStyle = .whiteLarge
    activityIndicator.color = UIColor.darkGray
    activityIndicator.alpha = 0
    activityIndicator.hidesWhenStopped = true
    
    return activityIndicator
}

private func centerActivityIndicatorInButton() {
    spinner.translatesAutoresizingMaskIntoConstraints = false
    
    let xCenterConstraint = NSLayoutConstraint(item: self, attribute: .centerX, relatedBy: .equal, toItem: spinner, attribute: .centerX, multiplier: 1, constant: 0)
    self.addConstraint(xCenterConstraint)
    
    let yCenterConstraint = NSLayoutConstraint(item: self, attribute: .centerY, relatedBy: .equal, toItem: spinner, attribute: .centerY, multiplier: 1, constant: 0)
    self.addConstraint(yCenterConstraint)
}

It works in case of calculating the center manually using this code.. But in case of rotation it's not working and it's not 100% accurate as we need to add 1point to width & height

let buttonHeight = self.bounds.size.height
let buttonWidth = self.bounds.size.width
spinner.center = CGPoint(x: buttonWidth/2, y: buttonHeight/2)

Thanks in advance for your time