Shaders causing ghosting on transparency

[Minerkey]

I'm working on a game with a friend (Shadows and Sickles) and I've been implementing a few visual things including an image-rounding shader. Issue is (and this is a problem I've encountered with other shaders too) that when dealing with transparent objects using image_alpha or any alpha thats not on the sprite itself, it'll often overlay a ghostly version of the viewport with the shader unapplied to it, as seen here on this scarecrow

Its an issue I've frequently run into and I have no idea how to go about solving it as I'm not very familiar with shaders. Any help would be appreciated!