A few things I would check:
- Do you have a lot of link tracking calls? Link tracking calls removes pageName and pageURL.
- Do you have an implementation that tampers with pageURL at all? The pageName variable falls back to pageURL. Try navigating through your site in IE11 and make sure all variables are working using the Adobe Analytics debugger.
- Are you on the latest AppMeasurement version? Numerous fixes have been applied over the months and years to resolve issues like this.