Some examples... clicking on a pin brings up the title of the pop up, which one then tries to "swipe" up on, but instead you must tap it.
Clicking on a pop up and viewing the image attachment opens in a new window, which can be tricky to find your way back to the previous tab.
Getting in and out of widgets often leaves you stuck, as one would normally tap outside the widget to close it and move on, but instead you must re-tap the widget. Sometimes elements of the UI get stuck... such as in the Nearby app (image below). And so on.