Client could not access the remote application. Changing Connection Mode temporarily fixes this

Using Parallels Client V17 to connect to RAS also V17. The client recently started saying "[516] The Client could not access the remote application. The machine might be too busy..." when attempting to start any published apps. Changing the Connection Mode between Gateway SSL and Direct SSL temporarily fixes the issue, but after a while (couple of hours) the issue comes back.
Only possible thing we can think of is that the organisation changed from Symantec to McAfee recently on the client computer, but this issue didn't immediately start when the change occurred.
Anyone have any ideas on why this is happening?
Cheers!