In the screencapture I first paint notes with swing grid disabled (0%), mouse modifier: Paint straight line of notes. Ok.
Then I do the same with a swing grid set, as can be seen it doesn't produce a contigous line (as would be expected?).
R6.03, Win8.1x64
sidenote:
I know I'm sloppy there with keeping vertical position hehe, but that shouldn't affect things should it?
edit:
maybe better one: