I have a couple of these devices doing the same thing. I did a glass replacement and the touch will work for a minute but once you press down slightly on the glass it makes the digitizer go crazy. I have it happening to three different devices right now. They were working fine until I needed to use the part for another device.
I have repaired the same HTC Evo 3D for someone four times now because of phantom touches or other issues with the digitizer. The last time it worked for 6 months before happening again. The device does not make it easy to get everything exactly where it goes but thankfully now you can get another device for $50-$80 if you feel like throwing the one you are working on across the room.
I was replacing a back camera on an iPhone 5 and after putting it together the device was searching for service all the time even after the basic troubleshooting tips. I even put the entire logic board in another iPhone 5 that had been working and it is still happening. Is it possible that their sim card needs to be replaced or the phone needs to be restored?