UITabBarController Subviews Don't Appear Weirdness - objective-c

Question

I have a curious issue with an iOS 9/ObjC app I am writing using a 4 tab format. The "main" ViewController has several subviews with controls and an image. When the user taps the image a PickerView pops up and it is dismissed with another tap on the image. The other tabbed ViewControllers lead to simple views. It was all put together with IB, except for a single subview on the "main" view where I do some Quartz animation drawing superimposed on the image view there.
If I stay on and interact with just the "main" view, all works exactly as desired. The PickerView appears and disappears as designed. Tabbing to another ViewController, then back to the "main" View leads to the problem: A tap on the image view fails to pop up the Picker. The tap is recognized in the Quartz layer, fires a Notification event which is picked up in the picked up in the main view controller which in turn adds the picker subview, brings it to the front and enables interaction just as when it works properly, but the picker never appears, even though the Debugger shows it successfully added to the subview array.
Even stranger, if I tab off the main to any other tab view, then back to main, the picker now appears again as it should. This sequence is completely repeatable - tab once off the main, and the picker doesn't visualize, tab again and then back to main and the picker works.
Any thoughts on where to start looking? Thanks
Here's some code (but I'm not sure where the problem is)
#implementation MainViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.picker = [[UIPickerView alloc] init];
self.picker.datasource = self;
self.picker.delegate = self;
float screenWidth = [UIScreen mainScreen].bounds.size.width;
float pickerWidth = screenWidth * 3 / 4;
// Calculate the starting x coordinate.
float xPoint = screenWidth / 2 - pickerWidth / 2;
[self.Picker setFrame: CGRectMake(xPoint, 50.0f, pickerWidth, 250.0f)];
[self.Picker setClipsToBounds:NO];
[self.Picker setBackgroundColor:[UIColor whiteColor]];
self.Picker.showsSelectionIndicator = YES;
self.Picker.userInteractionEnabled = YES;
.
.
.
UIImage *base = [UIImage imageNamed:#"Base"];
self.baseAView = [[UIImageView alloc] initWithFrame:imFrame];
[self.baseView setImage:base];
[self.view addSubview:_baseView];
self.GView = [[GView alloc] initWithFrame:imFrame];
self.GView.backgroundColor = [UIColor clearColor];
[self.view addSubview:_GView];
}
-(void) viewDidAppear:(BOOL)animated {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(doSin) name:#"touchP" object:nil];
}
- (void) doSin {
// user hits GView, draw Picker if not in View Hierarchy, if in Hierarch, grab value and resign
NSArray *subViews = [self.view subviews];
__block NSInteger foundIndex = NSNotFound;
[subViews enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if ([obj isKindOfClass:[UIPickerView class]]) {
foundIndex = idx;
// stop the enumeration
*stop = YES;
}
}];
if (foundIndex != NSNotFound) {
// Found the UIPickerView in subviews, so grab value & remove from screen
[self.view.subviews[foundIndex] removeFromSuperview];
} else {
// not in hierarchy, so put it up on screen
[self.view addSubview:self.Picker];
[self.view bringSubviewToFront:self.Picker];
self.view.userInteractionEnabled = YES;
}
}