I don't know if it's a know issue, but it seems that the contour from
pencil, paintbrush and rubber are being wrongly drawn on the screen
(using latest git version).
A video is available at http://sites.google.com/site/naoliv/gimp
demonstrating this issue.
See that when using the pencil, the "round" contour isn't symmetric as
it should be. For the paintbrush and the rubber the contour keeps
changing with every move.
It's a little annoying and makes us think "Why it's drawing outside
the contour?" or "Why it's not drawing where it's supposed to?"
Gimp-developer mailing list