Possible bug in "cloud" view


I have got an strange error that could be a bug. In my system there are several users (it’s a server for educational purposes). In a specifici group, for example, “AA”, all users have configured the same view, in this case, “cloud” view. But, for any reason I don’t know, some users don’t see the VNC button when their VMs are running, so they can’t connect with VNC. Other users, in the same “AA” group work fine and they get VNC icon.

All users create instances in the same way, because teacher instruct students with a “how to”.

However, if affected users change their cloud to “user” cloud, they can see “VNC” button with no problem…

Why? Maybe is there a bug in “cloud” view?