Blank screen, only mouse cursor - no warning

Hi, I'm using FSlogix Profile Containers on Windows 10 domain joined computers. Version 2.9.7654.46150

Registry settings
Profiletype value 0 (normal behavior)
PreventLoginWithFailure value 1 (enabled)
PreventLoginWithTempProfile value 1 (enabled)
DeleteLocalProfileWhenVHDShouldApply value 1 (enabled)

Expected scenario
What I want to achieve is that when a user logs in to computer A and does not log off and then wants to log on to computer B, a message should appear that the user is already logged in (or at least a error saying the profile-vhd is locked)
The PreventLoginWithFailure should display a warning on computer B when the user tries to log in.

Actual scenario
The user gets a black screen with only a mouse pointer which doesn't change when he logs on to computer B. To continue the user can use CTRL-ALT-DEL to log off.
During the login attempt (which failed / did not complete / stalled) a local folder was created for the user on computer B. Strange, the PreventLoginWithTempProfile setting should prevent this. right?
The user then logs off on computer A, the Profile VHD is no longer locked, and logs on to computer B.
The DeleteLocalProfileWhenVHDShouldApply settings does its job and removes the local userdir on computer B and the profile loads correctly.

Question
Why am I getting a blank screen (black, only mouse cursor) and no warning that the VHD is already in use (locked)

Hope that someone can help me.

Thank in advance.