Toolbar button unresponsive after iOS 13.4.1 update - objective-c

Question

I have had a medical calculation app for cardiac ultrasound in the App Store since 2011. At the bottom of each data entry screen is a toolbar with buttons to analyze all data, designate the open calculation as a favorite, and clear all active data from all calculations. After the most recent iOS update to 13.4.1, the Clear button at the bottom right of the screen has become unresponsive. If I put the app in the background, open another app, and then switch back to my app, then the Clear button becomes responsive again. If I move the Clear button to the left side of the toolbar, next to the Analyze button, then it functions without a problem. Since the code that displays these buttons has been the same for years and multiple iOS versions, I am wondering if possibly there is a bug in iOS 13.4.1 causing this issue.
Here is the code used to generate the toolbar:
//Initialize the toolbar
toolbar = [[UIToolbar alloc] init];
toolbar.barStyle = UIBarStyleDefault;
//Set the toolbar to fit the width of the app.
[toolbar sizeToFit];
//Caclulate the height of the toolbar
CGFloat toolbarHeight = [toolbar frame].size.height;
//Get the bounds of the parent view
CGRect rootViewBounds = self.parentViewController.view.bounds;
//Get the height of the parent view.
CGFloat rootViewHeight = CGRectGetHeight(rootViewBounds);
//Get the width of the parent view,
CGFloat rootViewWidth = CGRectGetWidth(rootViewBounds);
//Create a rectangle for the toolbar
CGRect rectArea = CGRectMake(0, rootViewHeight - toolbarHeight - [sharedVariableState g_toolbar_adjuster_for_Home_indicator], rootViewWidth, toolbarHeight);
//Reposition and resize the receiver
[toolbar setFrame:rectArea];
//Create two buttons separated by spacer item.
UIBarButtonItem *analyzeButton = [[UIBarButtonItem alloc] initWithTitle:#"Analyze" style:UIBarButtonItemStylePlain target:self action:#selector(analyze_clicked:)];
UIBarButtonItem *clearButton = [[UIBarButtonItem alloc] initWithTitle:#"Clear" style:UIBarButtonItemStylePlain target:self action:#selector(clear_clicked:)];
//Use this to put space in between your toolbox buttons
UIBarButtonItem *flexItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults]; //Load NSUserDefaults.
NSMutableArray *objectArrayMutable = [[NSMutableArray alloc]init];
objectArrayMutable = [[prefs objectForKey:#"savedFavoritesArray"] mutableCopy];
int favoriteChosenAlready = 0;
if ([objectArrayMutable count] > 0) {
for (int arrayCounter = 0; arrayCounter < [objectArrayMutable count]; arrayCounter++) {
if ([[objectArrayMutable objectAtIndex:arrayCounter] integerValue] == 58) {
favoriteChosenAlready = 1;
}
}
}
UIButton *favButton = [[UIButton alloc] init];
if (favoriteChosenAlready == 0) {
//Display empty star.
[favButton setImage:[UIImage imageNamed:#"Star_button_empty.png"] forState:UIControlStateNormal];
}
else {
//Display filled star.
[favButton setImage:[UIImage imageNamed:#"Star_button_filled.png"] forState:UIControlStateNormal];
}
[favButton addTarget:self action:#selector(favorite_clicked:) forControlEvents:UIControlEventTouchUpInside];
[favButton setFrame:CGRectMake(280, 25, 30, 30)];
UIBarButtonItem *favoriteButton = [[UIBarButtonItem alloc] initWithCustomView:favButton];
[[UIBarButtonItem appearance] setTintColor:[UIColor lightGrayColor]]; //Make toolbar button text lightGrayColor.
[toolbar setItems:[NSArray arrayWithObjects:analyzeButton,flexItem,favoriteButton,flexItem,clearButton,nil]];
//Add the toolbar as a subview to the navigation controller.
[self.navigationController.view addSubview:toolbar];
To clarify, the Clear button here now is unresponsive:
[toolbar setItems:[NSArray arrayWithObjects:analyzeButton,flexItem,favoriteButton,flexItem,clearButton,nil]];
However, just rearranging the sequence of buttons in the toolbar fixes the problem:
[toolbar setItems:[NSArray arrayWithObjects:analyzeButton,clearButton,favoriteButton,flexItem,flexItem,nil]];