Macbook Pro 2015 login screen glitch

Hi,

I have a MacBook Pro Retina, 15-inch, Mid 2015 and the login screen is distorted. I am running El Capitan Version 10.11.4

After a restart or shutting down the login user screen wallpaper is completely distorted with large chunks or red across it. There is a rough outline of my original wallpaper after logging in.

When I login to my account any distortion or glitch is no longer there and if I log out of my account the log in screen is absolutely fine.

Do you think this is a software glitch or physical damage?

Cheers,

James