Freehand lines snapping to something -- can't tell what

Hi, I’m new to the forums, so forgive me if this answer has been posted. If that is the case, could someone just point me in the right direction.

I’m using Graffle Pro to create a map. When drawing a river, I’m using the line tool and clicking multiple points along the way to simulate the wiggly flow of a river. Now, at times as I draw, the point seems to snap to a grid, so at times I get smooth wiggle, smooth wiggle, SNAP left or right, smooth wiggle, etc. I have align to grid off, I am not using any guides, so I don’t think I’m being pulled towards a guide… when this happens, those light blue ‘alignment’ lines show up as the next point is being ‘guided.’ As if it was telling me 'well, if your point is over here, it will line up with this object off-screen… so, let’s do that."

I can’t figure out why this happens at all. What should I be checking?

Did I ask the wrong question? Can anybody help me?

As a newbie I have the same question I guess. I cannot seem to create a smooth freehand object. It somehow ends up looking blocky so I am sure I am doing something wrong but cannot find anything in the manual.