FSLogix: frx.exe copy-profile error: Error copying profile (0x00000001): Incorrect function

Question

I want to convert a local profile into a VHDX file with FSLogix.

I am logged in as administrator and execute the following command:

frx copy-profile -filename=\\path\user.vhdx -username=domain\user -dynamic 1 -verbose

The programme starts the conversion, but at the end I always get the following error message:

...
Exporting registry information
Export Profile registry data error: 0x00000001
Error copying profile (0x00000001): Incorrect function.

Unfortunately, I can't see anywhere what causes this error and the VHDX file is not created.