I have been testing the latest build of Qt 5.5.1 for winphone_arm, trying to deploy my project to a WP 8.1 device. The package used was this one:
http://download.qt.io/snapshots/qt/5.5/5.5.1/147/

I get the following error:
"error APPX1101: Payload contains two or more files with the same destination path 'Qt5Core.dll'. Source files: "

This is reproducible every time, even for a clean project and after a complete re-build. Re-generating the same project using 5.5.0 (commercial) does work as expected so this is a regression.