I confirm that now I'm able to correctly connect to all the three vms in this environment where I have dns in place.
I also see that the icon at the right of the VM line has changed from "UP"/"DOWN" to a coloured triangle icon: nicer
And I confirm that the problem was the same for the other environment without dns in place where I have to use ip based information and disable https.
In fact all the 4 VMs have >= 2Gb of ram configured and so the problem arose for all of them. Now I can click on all of them and see their information without crash of the app.