Old thread, but did you ever find an answer to this? Having the same problem suddenly on a 2012 R2 RDSH with unlimited connections configured. 110 users. Never had this problem until this week, been in production for 6 years.
I run a Linux server with several VMs on it, and a pfSense box with HAProxy.
That allows me to access the services from outside with HTTPS, and manage certificates etc. in on place.
As a host, Linux outperforms Windows easily, and it's also free.
Firstly, are the custom AD groups landing in the correct local group on the affected servers? If they've been added, you should see them in Computer Management on each box. You may be running into delays with replicating the new groups before your task sequence adds them.
If you can, I suggest that creating the groups be the first task in your sequence. ...
After a quick read of your issue I suspect that it is group policy related.
If you configure Group Policies correctly, they provide a stable secure reliable environment
There are a number of areas that need be taken into account
• Enabling Remote Desktop on the Computer
• Who is allowed to do this?
• Are you using firewalls
I have a single GPO which ...
I have no reputation to comment so I post as an answer. Some of sites are known to perform a port scan of localhost: