How can I get rid of these dark lines in my pattern?
They only appear when I apply some sort of blend mode to my objects. These particular objects have multiply blend mode applied to them and the dark lines appear where the pattern "connects" in a grid.
I don't want to get rid of the blend mode, I need it for the desired look, but it's definitely the thing that causes the lines. Any advice?
The swatch looks like this. It seems like an overlap to me too, but I created the box as a 6x6 square and duplicated objects by moving them by exactly 6 inches. Also in the Pattern tool I set 6 inches as the size of the tile. What's interesting is that when the Pattern tool shows me the preview of how the pattern will look, there is no overlap. Even when I set 9x9 preview so there are many repeats. It only shows later when the pattern is applied to a shape.
Edit > Flatten Transparency
. This will alter the objects, So try it on a copy of the art first. If there is no transparency on the pattern tile itself, then this 1-2px anti-alias area won't be a problem. I can't say for certain this will work. I've honestly never used transparency in any pattern tile the way you are.