Contour tool is behaving irregular when drawing a single pixel. “Dotting” out a pixel with contour tool is possible, but “contouring” out a single pixel (click and draw inside a single pixel) doesn’t draw anything.
Tested and worked in version 1.2.9.
Did a report of this on discord, but figured that it’s easier to track here.
Thanks for reporting this @vigge, I was able to reproduce it, it happens only when you move the mouse inside the same pixel 
We’ll try to fix it for the next version!
Tested the fix in v1.2.14-x64.
Even though it’s much better, the issue still persists. However, it is much less frequent now but that also means that it is more difficult to reproduce.
The best way for me to reproduce it [inconsistently] is to fast-click single pixels randomly over a small area with the Contour tool and roughly 10% of them wont be drawn.
Sorry for the vague report. I’ll update if I find a better way to reproduce.
Sorry about this, but I forgot to mention what you have just found. Before releasing v1.2.14 I noticed the same problem: the contour for just one pixel doesn’t work in some extreme cases of one click. Hope to have a fix for 1.2.15 this week.
Ah! Great news 
Looking forward to it