Issue with border color of image in PIL

I'm having an issue with a PIL image that I'm creating. It seems as if the border edges of the grey background is taking the colour of the ellipse drawn on top of the background.

Firstly, I'm using a helper function to allow for a smoother looking ellipse by using antialias. However, I think the mask in this helper function is causing an issue where it's leaving an very small (green) outlined in each corner of the of the gray background.

For my corners I'm using another helper function to create these. Maybe there is some confliction with both functions here but I'm not too sure.

Here is what I am trying to do:

def draw_ellipse(image, bounds, width=1, outline='white', antialias=4):
    """Improved ellipse drawing function, based on PIL.ImageDraw."""

    # Use a single channel image (mode='L') as mask.
    #The size of the mask can be increased relative to the imput image
    # to get smoother looking results. 
    mask = Image.new(size=[int(dim * antialias) for dim in image.size], mode='L', color='black')
    draw = ImageDraw.Draw(mask)

    # draw outer shape in white (color) and inner shape in black (transparent)
    for offset, fill in ( -7, 'white' ), ( width, 'black' ):
        left, top = [(value + offset) * antialias for value in bounds[:2]]
        right, bottom = [(value - offset) * antialias for value in bounds[2:]]
        draw.ellipse([left, top, right, bottom], fill=fill)

    # downsample the mask using PIL.Image.LANCZOS 
    # (a high-quality downsampling filter).
    mask = mask.resize(image.size, Image.LANCZOS)
    # paste outline color to input image through the mask
    image.paste(outline, mask=mask

def add_corners(im, rad):
    circle = Image.new('L', (rad * 2, rad * 2), 0)
    draw = ImageDraw.Draw(circle)
    draw.ellipse((0, 0, rad * 2, rad * 2), fill=255)
    alpha = Image.new('L', im.size, 255)
    w, h = im.size
    alpha.paste(circle.crop((0, 0, rad, rad)), (0, 0))
    alpha.paste(circle.crop((0, rad, rad, rad * 2)), (0, h - rad))
    alpha.paste(circle.crop((rad, 0, rad * 2, rad)), (w - rad, 0))
    alpha.paste(circle.crop((rad, rad, rad * 3, rad * 3)), (w - rad, h - rad))
    im.putalpha(alpha)
    return im

    #Grey background
    im = Image.new("RGBA", (900, 296), (44, 44, 44, 255))
    #Add some corners
    im = add_corners(im, 50) 
    im_draw = ImageDraw.Draw(im)


    #Green Ellipse
    ellipse_box = [55, 37, 107 + 48 + 46, 103 + 80]
    draw_ellipse(im, ellipse_box, width=20, outline=(52, 235, 52))

    im.save("image.png")

Output: