This has happened many times in the past and have never been able to resolve. Another thing to note is that originally the image is a square, I just added a UICorner to it to make it round.
I believe this is a bilinear interpolation error/bug causing transparent pixels to create those white borders when scaling image elements with ROBLOX studio. What I’ve found that works for me is running the images through PixelFix (Windows) or Alpha Bleed (browser based).