This not an RC meeting issue, its an RDP issue - you will need much more memory on your server and also require dedicated video memory on your server as well to improve this. We have setup many RDP servers and attempted to get video conferencing working, but it always ends up not justifying the costs (each user that video conferences on the server slows down or freezes all other users on the server, video conference quality at both ends is very poor quality and very unreliable as to whether it will work each time you use it because other running programs and users on the server are unknown each time,....)
The most reliable approach we have found is to have our users do all their work on their RDP server sessions and all video conferencing / video streaming (training, news,...) be performed on their local laptop/computer. They can still screen share the RDP session if required, so there is no loss of functionality and does not affect or rely on the servers current state of all the users.
Again, this is the same exact problem with all video conferencing on an RDP server (RC Meeting, Zoom, Webex, Google Meet, MS Teams, ....)