We have 2 network users that are in NPS adding radius clients at the same time as we have a lot of radius clients to add. They both have the exact same permissions, however when one user adds radius clients, they disappear, the other user's additions do not.
A) Is there a limit of how many users can add NPS clients at the same time?
B) Is there a limit of radius clients that can be added in Server 2012?
Which edition you are running?
According to the article below, with NPS in Windows Server 2008 Standard, you can configure a maximum of 50 RADIUS clients and a maximum of 2 remote RADIUS server groups. And no limitation for Windows Server 2008 Enterprise and Windows Server 2008 Datacenter.
Since the article was updated and applied to window server 2012. So I think it should be the same in window server 2012.
Network Policy Server Operations Guide
Hope this helps.