How to get a fresh session for each user connecting via VNC

Question

I am developing cyber ranges for my college. I am using guacamole and docker to run the environment. I was able to create a VNC connection to the attacker machine via guacamole. But I am not able to achieve user isolation, ie. if multiple users start the lab they should get a fresh screen, instead the same session is being reflected on all the logins. How can I do that?

I tried researching on same but did not find anything useful.