Wacom pens left-click stops working when I use Lightroom

Hi, I have a Wacom Intous Pro tablet (M, PTH 660) and I work a lot in Lightroom on my iMac. For a long time now, the pens left-click stops functioning every now and then. Right click is still working, and I can move the pointer/arrow. The only way to solve the problem is then to restart the mac. 

Lately this happent a couple of times every day, and it has become a big problem.

I have tied 2 times to reinstall the wacom driver (properly uninnstalled the old one), but this does not solve the problem. I find it very strange. It usually happens when I adjust the Texture button in Lightroom!

Has anyone had this problem, and most importantly, can it be fixed?