I discovered that when you close the app on an iPad (as opposed to sleep), then open it, sometimes the Action Buttons (and Feedback Action Buttons) are non-responsive (they don't do anything). This can be cleared by opening another page (even a blank one), then returning to the initial page.
I was able to demonstrate this by creating a page with a single button (B-1), and using the provided LocalExample.py on the server.
Closing the app by doubleclicking the home button, then opening the app, should demonstrate the problem. However, it doesn't always! The attached page (test002.xml) shows the problem on my iPad - don't know if it will elsewhere.
Sometimes adding a second button clears the problem - sometimes not. I was finally able to resolve the problem on my page (which has around 20 buttons) by renaming B-1 to B-91.