Hi, I did find a post that addresses my question but wasn't really answered--OP just had a 'workaround'.
Sometimes when I create a pattern using a clipping mask to remove extraneous bits outside of the square (that will be the swatch), the resulting swatch has a lot of white space around it and the pattern doesn't abut--the repeating images have blank spaces around them.
I am simply using unadulterated vector lines and shapes for the pattern--no raster--and an unstroked unfilled square.
if you use a clipping mask, the element are still captured in the pattern. look at your tile in outline mode to get a better understanding of the issue. i always check my pattern in outline mode before dragging it to the swatch palette.
the shortcut for outline mode is Cltr+Y and hit it again to go back.
I hope this answers your question. if not flame away