Unassigned Pad caused a total Crash

Using Chord Pads I try to clear some chords by Right click and select unassigned pad, the first one was removed trying to do a second one and I had my first total crash.
On restarting the project all the changes I did on the chord pads disappeared, had to do them all over again.

New MBP Retina 2014 with i7 2.5
New install of Cubase 8
New Project
No plugins used in project
Sampletank 3 is the only plugin installed.