Pixelated Loading Screen?

Hi, I've recently updated my Mid-2014 MacBook Pro with Retina Display to Sierra, and my logins have been a bit pixelated, what I mean that is I've had retina display for the first few seconds, then the screen goes a little pixelated, where it looks like there's no retina display. As soon I'm done logging in, it goes away. Only happened after updating to Sierra.