Scrolling gets "stuck" when using nested scroll views

Problem description:

I have one iOS project for browsing images with nested UIScrollViews which is inspired by famous Apple's PhotoScroller. The problem is what sometimes scrolling just "stuck" when image is zoomed width- or height-wise. Here is an example of how it looks on iPhone 4s for image of size 935x1400 zoomed height-wise:

(I start dragging to left, but scroll view immediatly discard this action and image get "stuck")

Workaround:

I found kind of workaround by adjusting content size of inner scroll view to nearest integer after zooming:

// Inside ImageScrollView.m

- (void)setZoomScale:(CGFloat)zoomScale
{
    [super setZoomScale:zoomScale];
    [self fixContentSizeForScrollingIfNecessary];
}

- (void)zoomToRect:(CGRect)rect animated:(BOOL)animated
{
    [super zoomToRect:rect animated:animated];
    [self fixContentSizeForScrollingIfNecessary];
}

- (void)fixContentSizeForScrollingIfNecessary
{
    if (SYSTEM_VERSION_LESS_THAN(@"10.2"))
    {
        CGSize content = self.contentSize;
        content.width = rint(content.width);
        content.height = rint(content.height);
        self.contentSize = content;
    }
}

But this fix not perfect - some images now are shown with one-pixel wide stripes on sides. For example, on iPhone 6 for image of size 690x14300 it shows this at the bottom:

Also, oddly enough, I'm able to reproduce this problem on iOS 7.0 - 10.1, but everything works correctly on iOS 10.2 and greater.

Question:

So, what I am doing wrong? Can my fix be improved?

Test Project:

I created simple test project to illustrate described problem - NestedScrollingProblems. Please note what my version of ImageScrollView is slightly different from Apple's one because I applied another rules for zooming. Also, workaround is commented out by default. (project code is a bit messy, sorry about that)