brush+SHIFT command acting really weird

[ziggie]

So, when I use paint brush and I combine it with SHIFT key for more precise stroke I get this really weird bug with the stroke. Bug is essentially a double line , double stroke being performed usually NOT in the desired direction. Stroke I wanted to make is made but second stroke follows it and it usually goes in the opposite direction, sometimes diagonally straight across the whole canvas, a lot of times it just jumps vertically regardless of the '' required '' direction. Hope i explained it well, I don't really know what could this be, I thought that maybe SHIFT command is slightly over-reactive, it's really good to have such a precise tool, but sometimes it produces unwanted results All best, Peace.

[support]

Can you save a video from screen to show what's happens?