Sample MapView to replicate a bug (http://stackoverflow.com/questions/33546930/mkmapview-center-not-correct)

gistfile1.m

#import "ViewController.h"
#import <MapKit/MapKit.h>

static CGFloat kCMStartY = -150;

@interface ViewController ()

@property (nonatomic, strong, nullable) MKMapView *mapView;
@property (nonatomic, strong, nullable) UIView *mapViewContainer;
@property (nonatomic, strong, nullable) UIView *squareView;

@property (nonatomic, strong, nullable) UIView *overlayView;

@property (nonatomic, assign) CGFloat currentY;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    self.mapView = [MKMapView new];
    
    self.squareView = [UIView new];
    self.squareView.backgroundColor = [UIColor orangeColor];
    
    self.currentY = kCMStartY;
    
    self.mapViewContainer = [UIView new];
    [self.view addSubview:self.mapViewContainer];
    [self.mapViewContainer addSubview:self.mapView];
    [self.mapViewContainer addSubview:self.squareView];
    
    self.overlayView = [UIView new];
    [self.view addSubview:self.overlayView];
    
    UIPanGestureRecognizer *panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panGestureRegognized:)];
    [self.overlayView addGestureRecognizer:panGestureRecognizer];
    
    [NSTimer scheduledTimerWithTimeInterval:0.5
                                     target:self
                                   selector:@selector(timerFired) 
                                   userInfo:nil
                                    repeats:YES];
}

- (void)viewDidLayoutSubviews {
    self.overlayView.frame = self.view.bounds;
    
    self.mapViewContainer.frame = CGRectMake(0, self.currentY, CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame));
    
    if (!CGRectEqualToRect(self.mapViewContainer.bounds, self.mapView.bounds)) {
        self.mapView.bounds = CGRectMake(0,
                                         0,
                                         CGRectGetWidth(self.mapViewContainer.bounds),
                                         CGRectGetHeight(self.mapViewContainer.bounds));
        
        self.mapView.center = CGPointMake(CGRectGetMidX(self.mapViewContainer.bounds),
                                          CGRectGetMidY(self.mapViewContainer.bounds));
    }
    
    self.squareView.bounds = CGRectMake(0, 0, 22.0f, 22.0f);
    self.squareView.center = CGPointMake(CGRectGetMidX(self.mapViewContainer.bounds),
                                         CGRectGetMidY(self.mapViewContainer.bounds));
}

- (void)timerFired {    
    [self.mapView setRegion:MKCoordinateRegionMake(CLLocationCoordinate2DMake(51.501367, -0.141744), MKCoordinateSpanMake(0.015, 0.015))];
}

- (void)panGestureRegognized:(UIPanGestureRecognizer *)panGestureRecognizer {
    CGPoint translation = [panGestureRecognizer translationInView:self.overlayView];
    
    CGFloat y = kCMStartY;
    if (panGestureRecognizer.state == UIGestureRecognizerStateBegan ||
        panGestureRecognizer.state == UIGestureRecognizerStateChanged) {
        y = translation.y;
    }
    
    self.currentY = y;
    
    [self.view setNeedsLayout];
}

@end