Some WMI calls to Unified Write Filter (UWF) return Access Denied errors

I am currently working on a C++ application which uses the integrated write filter(UWF) of Windows 10 IoT.

I am using Windows 10 IoT Enterprise LTSC 1809 Build 17763.107

Now I face the following problem: Some WMI calls return with a "0x80041003 - Access denied" error and I can't figure out why. I have no problems to enable and disable the filter, commit files, query exclusions and even shutdown or reboot the system. But whenever I try to add or remove exclusions (file or registry), protect or unprotect a volume or enable the servicing mode I get the access denied error.

I have already tried/looked into the following things:

1. The program is run locally from administator console with elevated rights
2. The user account control (UAC) is deactivated
3. COM security settings are (presumably) correct (dcomcnfg)
4. WMI namespace permissions are (presumably) correct (WMImgmt.msc)
5. WMI impersonation rights are (presumably) correct (gpedit.msc)
6. The Administrator is in the Administators group (lusrmgr.msc)

The problem occurs with C++, C#, PowerShell and the WMI testtool (wbemtest). The only working way I found was the uwfmgr.exe.

My question is now how do I get the WMI calls to work properly? Are there any further setting I missed so far or are some of the WMI calls just not working?

Any ideas or suggestions are welcome!