Pen is always drawing
I have experienced the same problems in the aforementioned cases about the pen randomly highlighting things on the desktop/making selections, as well as loss of double tapping feature for double clicking. For my situation, I am pleased to say that I've managed to resolve the problem it may or may not help but worth a try. The solution:
(1) go to control panel and open up the 'Pen Tablet' icon,
(2) under 'Tracking' select 'Pen Mode' and click on 'Details' tab,
(3) under 'Screen Area' select 'Monitor' (*IMPORTANT*)
(* other settings I have are: 'unchecked' force proportions, 'Tablet Area' set to 'full', number of monitors under 'Screen Area' set to 1)
Following the above steps should remedy the problem. It worked for me. I hope it proves useful to you as well.