Programmatic Device Specific iOS Constraint is nil

I came across an interesting problem that only arises on iPhone 6/6+ and iPad mini with retina display.

In the following code:

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    if(self.seeMoreContents)
    {
        BOOL isText = [self.seeMoreContents isText];
        self.imageView.hidden = isText;
        [self.textView removeConstraint:self.textHeightConstraint];
        [self.textWrapperView removeConstraint:self.textWrapperHeightConstraint];

        if (!isText)
        {
        __weak FCSeeMoreViewController *weakSelf = self;
            [self.imageView setImageByFlashcardSide:self.seeMoreContents completion:^(BOOL preloaded){
                weakSelf.imageView.center = CGPointMake(weakSelf.view.frame.size.width / 2, weakSelf.view.frame.size.height / 2);
                [weakSelf.scrollView setContentOffset:CGPointMake(0, 0)];
            }];
        }
    }
}


- (void)viewDidLayoutSubviews
{
    if ([self.seeMoreContents isText])
    {
        self.textView.text = self.seeMoreContents.text;
        self.textView.font = self.fontForContents;

        self.textWrapperView.hidden = NO;
        [self.textView sizeToFit];
        CGFloat height = self.textView.frame.size.height;
        [self updateView:self.textView withConstraint:self.textHeightConstraint ofValue:height];
        [self updateView:self.textWrapperView withConstraint:self.textWrapperHeightConstraint ofValue:height + self.wrapperMargin];

        [self.scrollView setContentSize:CGSizeMake(self.textView.frame.size.width, height + self.scrollTextMargin)];
        [self.scrollView setContentOffset:CGPointMake(0, -self.wrapperScrollVerticalConstraint.constant)];
    }
    [super viewDidLayoutSubviews];
}

- (void)updateView:(UIView*)view withConstraint:(NSLayoutConstraint*)constraint ofValue:(CGFloat)value
{
    constraint.constant = value;
    [view addConstraint:constraint];
}

By the time the two messages of udpateView get passed, the constraints have become nil. I could attribute this to weird garbage collection behavior, but it only happens on iPhone 6/6+ and mini retina iPad.

I have changed this whole controller to work better and to not to programmatically set constraints, but I want to know how/why this can happen on specific devices. Any insight would be greatly appreciated.