UISlider disabled state blur issue with @3x graphics only (iPhone 6 Plus)

I have an issue with UISlider thumb image in disabled state on iPhone 6 Plus only (@3x graphics). I'm only setting the normal state image and letting the system render the disabled state. Normal state looks just fine on all devices. The disabled state blurs the thumb image correctly on other devices but not on iPhone 6 Plus, the blurred image looks a bit rough on the edges of the thumb image. Is there a way to fix it so the normal image is adjusted and blurred like on other devices?

Link to the rendered thumb images