I read of similar issues in the past, but none seems like mine. If I leave x2goclient running and I don't use my PC for a while (like half an hour or more) when I return I find sometimes it runs at 100% CPU. Killing and restarting it solves the issue, but usually it occurs some time for my machine to reply to input when it happens.
I have a Debian 10 (x2goclient 4.1.2.1) and I connect to the server (still Debian 10) by a Forticlient VPN and a Gnome session.
I could provide more information, if you told me how.