RDP Long delay between Longon-Event and GPO-Processing

Hello,

i have an 2019 rdp connection-broker and some 2019 session-hosts with current os.

Sometimes it takes a very long time (up to 15 minutes) between the logon at the session-host till i get an desktop.

In the event-log i see the security-event 4624 (an account was logged on) at 08:02.

If i check gpresult for this user i see the processing of the gpo startet at 08:16 and is finished in a few seconds.

And this times match with the user-experience that they see a "loading user profile" message.

How can i get information which task takes so long?

Regards

Arnold