I am now having the following issue related to UIScrollView. I have a horizontal UIScrollView in which I show cards, which are themselves vertical UIScrollViews. All this works fine, as expected. Here is where problems start to appear, when I become a "rough user": - I initiate a horizontal scroll and right after, before it finishes I tap quickly and continuously for a little while. - The scroll cannot finish, but more stangely: When I then scroll vertically, I noticed none of the delegate method are getting called, even scrollViewDidScroll. The app does not crash. When I scroll horizontally again, I get some little anomalies at first, certainly due to the fact some method were not properly called and then the app goes back to its normal functionning. Eventhough this happens only when the user is being a bit rough, this is annoying as a developper, not being able to secure the code. I did a lot of tracing to debug the code (for example check that the delegate for the vertical UIScrollView was still there) and find out where the problem was, but at this point with no success. Any suggestions?