I'm trying to use a single overland map in Decent into Avernus when I have the GM map and then overlay portions of the player map that I've cut out to block the players from seeing the location names until they are discovered.

However when I put the obscuring bit of player map as an image layer on top of the main Avernus map, I get this weird border of pixels that aren't in the actual image:
Capture.PNG

I'm aware the image isn't exactly positioned correctly above, but unless I can get rid of the border there's no point as it sticks out clearly and defeats the purpose. Note the reddish line on the right side, I've checked the image with several programs and the border of pixels just isn't there in the actual image file.

Am I inserting the image incorrectly or maybe some other way of fixing this?