Experience the same problem with:
OS X 19.9.4, Mac client X2Go Client V.4.0.2.0 (Qt - 4.8.5)

On the remote server I see one CPU completely killed:
PID USER PR NI VIRT RES SHR S %CPU %MEM    TIME+ COMMAND
21002 filer     20   0 63148 41m 5528 S 66.5 1.7   3:51.08 x2goagent
21323 filer     20   0 20936 4956 2516 S 15.3 0.2   0:53.50 xfce4-settings-
21303 filer     20   0 20336 8688 7120 S   0.7 0.4   0:02.84 xfwm4
21305 filer     20   0 35364 10m 8976 S   0.3 0.5   0:00.72 xfce4-panel

At the same time, as soon as I disconnect. CPU usage of x2goagent goes to 0.

Is it the case that Linux clients don't have this problem?

thank you,

Kirill