This came out when I tested my new tablet, a Wacom Intuos Pro. Although I also got myself the newest Photoshop version, too, I still have that bug where thick lines occur randomly while drawing. By setting the time for a double click to a minimum it got better, but the problem's still there.
picture shows howling-blackpaw and me moving some of my stuff to my future home in Germany (some boxes are obviously heavier than others ;) )