Edit @tacticallysrupid helped me fix it I had to remove all the 2nd vertices by selecting all the vertices, pressing m then clicking merge by distance then outlining a bit outside the uv map
check if your graphics driver on your pc has any updates!! you may be experiencing a common bug where the textures have a weird outline on them, is your computer old?? try publishing the game and joining it on your phone to see if the issue still persists
roblox automatically downscales images to 1024x1024 iirc, so this would have done nothing anyways. have you tried texturing this to a smaller size in blender instead??
have you tried looking at the mesh from another device?? it’s possible that there’s nothing wrong with the texture at all and it’s just your game bugging out.