Adjusting the cap style also fixed it.Originally Posted by Feralspirit
Another thing I found in tinkering around with it is that if you manually set the page size to something smaller than the whole image, it also fixes it. Essentially, you're cropping the image natively in Inkscape (as opposed to exporting it and then cropping it in GIMP).
I've included an un-cropped version of the map, in case anyone was curious as to what I am doing.