You gave me an idea to just make the game increase its canvas size slightly because my game is already programmed to handle different sizes of that with black bars on the side to make it visually appear still 256x224. This seems to have fixed it because the edges of the screen where the tilemap can't paste are never visible. Players likely will never notice it's been set to 262x224 or whatever I end up going with since it uses letterbox integer. As well as probably all monitors are wider than they are tall to begin with.
I need to use drawing canvas for this because sprites like the player and enemies also cast a drop shadow.