Bitmap pattern has seam ONLY when created with "Object → Pattern → Make"

Question

I think I've encountered a bug with Adobe Illustrator CC 2014.
I'm trying to make a repeatable pattern out of a bitmap, which I downloaded from http://subtlepatterns.com
Most of the patterns I try, work correctly, but one in particular behaves strangely.
(This is the png in question: https://dl.dropboxusercontent.com/u/473648/pw_maze_black.png, Here is an example AI file that shows the problem: https://dl.dropboxusercontent.com/u/473648/Pattern%20Seam%20Example.ai)
When I create a pattern with the "Object → Pattern → Make" menu item and then apply it to a shape, I get hairline seams that appear in the pattern at various zoom levels. If I export the file with "Save for Web" to a PNG then the seam disappears, though if I use the plain "Export" feature to create a PNG the seams appear in the output file.
The strange thing is when I create a pattern from the above PNG by dragging it to the Pattern palette and use that pattern, the seams do not appear in any export files, or in the design window of AI.
Other patterns I've tried from subtlepatterns.com work correctly when created with the "Object → Pattern → Make" menu item.
Obviously I have a solution to this problem, but is there an explanation for the difference between creating the patterns with the two methods, or is it a bug?
Thanks,
Caleb Land

Answer 1

When dragging the pattern to the swatches panel works, just do it. You don't need the pattern editing mode for this one.