Cannot use trackpad when I plug mouse, option to turn on grayed out

Hello,

I have new TP X1 Yoga (3rd gen) and whenever I have a mouse plugged, I cannot use the trackpad. This wouldn't be a problem, but since I have a wireless Logitech mouse, I tend to keep the wireless receiver dongle always on to avoid losing it, and even with the mouse tued off this disrupts the trackpad. 

Is this a known bug? Is there something I can do to fix it?

Cheers and thanks in advance,

Leo