System hang, 17.10

This morning for the first time since running Ubuntu Budgie 17.10 I experienced a system hang.
I was doing work, running Firefox, Slack (snap) and VMware Workstation.
I moved a VMware window around and nothing responded any more.

After a minute I pressed Ctrl-Alt-F1 to look what was going on and all of a sudden Budgie came back up with a login prompt.
I installed VMware workstation the day before, so that’s my primary suspect.
What would be a basic way to determine what went wrong?

I had several instability with Oracle VirtualBox ( system hang ) randomly…
UB 17.10 and 18.04

I would suspect VMWare too…