Qt Designer doesn't launch

Visual Studio 2015 Update 3
Qt 5.6.2 for Windows 64-bit (VS 2015)
Qt 5.7.0 for Windows 64-bit (VS 2015)
Windows 10 Professional 64 bit (Version 1607 Build 14393.321) german version:

Attention: This bug only happens if Qt WebEngine is installed!
This is propably related to QTBUG-53984 or QTBUG-54033.

Qt Designer only launches if started from within Qt Creator. Qt Designer doesn't launch:

1. If it is started via Visual Studio 2015 main menu 'Qt VS Tools / Launch Designer'.

2. In Visual Studio 2015 solution/project explorer: If a Qt form file is double clicked.
Nevertheless it is linked to Qt Designer as required.

3. If designer.exe is executed stand alone directly from Windows Explorer file manager.

Whereas Qt Linguist and Qt Assistant launch in any situation, even if their exe files are launched stand alone from Windows Explorer file manager.

This all happens no matter if you start Visual Studio 2015 as administrator or in an user account.