Here's the setup - I have a Windows Server 2019 environment with multiple users logging to their terminal sessions.
I myself log on to the server with a terminal session.
I have installed the RU Host on the server and use the RU Viewer to connect to sessions on the same server.
Look at what happens on the screencast
https://we.tl/t-X0W54OdR4XIt works sometimes, though and when it does, it works well.
Same happens in the stable version (6.10.10.0) as well as in version 6.12.1.0 (Beta 1).