Unfortunately its an on-going issue with the 1520. Very often you'll find that swiping the screen will result in an app or page opening because the screen interpreted the gesture as a tap rather than a swipe. And yes, occasionally the whole screen freezes up and the only corrective action is a reboot. I've had the 1520 from nearly day one of its launch (Dec 2013) and screen sensitivity/freezing issues have continued through various software updates and fixes. Another annoying screen issue I have is the delay in the light sensor adjusting the screen to the correct brightness levels.....you switch on your phone from sleep (or glance screen) mode and it takes a few seconds......sometimes up to 5 seconds.....before the screen brightens up.
We keep hearing that Nokia/Microsoft are well aware of these issues and that they may be addressed in future software updates. But frankly I'm sceptical.....only because I don't think the 1520 was a particularly big seller for Nokia and so many other Lumia's have launched over the past 6-7 months that the 1520 is no longer the flagship of the fleet.
Don't get me wrong, I love my 1520 and wouldn't trade it in for any other Windows Phone out there, it's an awesome bit of technology and the best phone I've ever owned, but I just don't see a screen sensitivity / light sensor performance improvement happening.
One thing that you can do is experiment with the screen sensitivity setting (setting - touch). Some people say it the situation improves if set to high, others (like myself) find the screen to be slightly better at reading my inputs when set to normal.
And don't forget to visit the windows phone contact us webpage and biiitch like hell about the problem.....that's what me and many others have done in the past and it's probably the only way we'll eventually get MS to find a fix
Cheers
applesux