The users should pay attention on old/lost X2Go sessions under theirs USER_ID in the project virtual machines. Normally, the user should have only one X2Go session which will create about 20-30 processes during its execution. If the user finds more than 30 processes relate to the X2Go session then it will be necessary to kill old/lost session (check how to kill processes here)
Closing/Finishing the X2Go
