Why is the ScrollView constantly going back to the top?

Question

iOS

I create a view, I put a scrollview inside (I stretch it to full screen and set the indents to zero).
I put a picture inside the scroll + label1 + label2
Label2 contains a long text (dynamically loaded).
I launch the application, everything is displayed as it should, but the scroll scrolls and when you release it, it returns to the top.
How to overcome it?
Tried self.scrollView.contentSize.height = 1500.00 - zero reaction