opening scanning dialog windows slow in one of our RDS 2012 server.

We have a few RDS 2012 R2 servers. When a user open an remoteapp and launches the scanner, the dialog windows takes 20 seconds to launch on this particular server. I have isolated this server and currently there are only one user and it's still slow. Everything else runs quick except when opening the scanner dialog window. I have updated the remote scan software and still the same.