Printing .png images - getting lines around image bounding box

[Robert Smith]

One of my hobbies is making my own stickers using my Canon Pixma Pro 100s and a vinyl cutting machine that I have. Every now and again when I'm printing an A4 sticker sheet, some of the images I'm printing from the sticker design software print out with thin black lines around two of the sides of the image. The lines correspond to the edge of the transparency.

This isn't a printer-related issue per se. I don't actually know why it's happening, I was just hoping that someone on the forum might have come across this before and have a solution.