Designer and Linguist: KERNELBASE!RaiseException on Windows 10

EDIT02: With 5.7.0 Final being out, I did more tests:

A.) I compiled a Debug Version of the Tools etc. When I do the following:
1.) Start Linguist.exe
2.) The UI shows up as expected. No Problem here yet
2.) Attach the Qt Debugger from within Qt-Creator to Linguist.exe or Start and Debug External Program
2.) Open a .ts File
3.) The App loads the File and shows the content
4.) 3-5 Seconds later, you can see "(Not Responding)" in the Window Title
5.) The small Message in the Qt-Creator Debugger Windows says:

warning: Exception at 0x7ffd2a891f28, code: 0x6ba: RPC server unavailable, flags=0x1 (execution cannot be continued) (first chance) in KERNELBASE!RaiseException

No further Error Messages or Debug Information are shown. Still a Beginner with Advanced Debugging: If there is anything that could help to get more Data (with Qt Creator 4.0.2), please let me know if you wish.

B.) I copied the whole Folder to a Windows 7 SP1 x64, all updates, clean Installation (no MSVC Redist, no Qt Stuff etc.) VM and the Release and Debug Executables are running fine. No Problem at all. I had to copy the VC Redist and the API-MS-*.dll Files manually of course too.

With Designer.exe on Windows 10:

• The Debug Version starts up just fine. But when select a .UI File and click or press Enter to opening it, the same Error Message comes up. But you can Edit and Save the File. Other Functions untested.

With Assistant.exe on Windows:

• The Release and Debug Version showing no Symptoms in the Debug Window. But I am not sure how to test those.

In addition.
A.) The same Problem exist in the 32-bit and 64-bit Binary Packages of the MSVC 2013 and MSVC 2015 Final Packages. The MinGW Versions are working as expected.
B.) I remember that I got some Error Message about $something not found in the COMDLGxx.DLL. But I could not reproduce this yet.
C.) I also did (for other Reasons) a Format of my HDD and a total Clean Installation of all my Software and Tools.

D.) The "Remote Procedure Call (RPC) (set to Automatic)" Service is running as it should
E.) I also started "Remote Procedure Call (RPC) Locator" Service (not running by Default, set to Manually): Still get the above Error Message.

When calling Designer.exe, the Process stays open until forever in the Windows Task Manager. No Error Message at all. Even calling

Designer.exe /?

to show all current known Parameters, just starts the Designer.exe Process but it does not show anything.

The Memory usage of Designer.exe starts at 16.5 and falls down ~7 Megabyte a couple sometimes later. CPU usage stays at 0 Percent. Disk usage is 0 Megabyte / second.
At this time, the Path to the Qt Custom Installation is not set. But even if the Path is set, it makes no change.

The Parameters to compile Qt are:

c:\qt5srcgit\qt5\configure -opensource -confirm-license -prefix c:\qt-build64test -opengl dynamic -debug-and-release -developer-build -openssl -I C:\opensslx64\include -L C:\opensslx64\lib -icu -I C:\icurlsx64\include -L C:\icurlsx64\lib -mp -nomake tests -no-warnings-are-errors