Unity 5.1 UI flickers when button pressed

Since I upgraded to Unity 5.1, everytime I press a button, the UI flickers. This is on android.

The same build with Unity 5.0 doesn't flicker. Now that I've upgraded my projects to 5.1, I can't go back. I'm close to a deadline and can't afford the UI to flicker everytime a button is pressed.

Any suggestions on how to fix this?