I'll try...

When i say 'Tempermental' I mean inconsistent.

You click the left button on the icon and nothing happens.  You click again  - nothing happens, you click a third or a fourth time and the command is active.

On other occasions is randomly activates on first trying.  As I say, this is not happening on any other software,  and it has never occurred on AutoCAD LT 2013,14,15,or 16.

Hope that helps.

Thanks Maxim

Neil