Inexplicable UI flickering in 5.1.0f3

After upgrading my project to Unity 5.1, some of my UI elements have begun to inexplicably flicker and disappear at random. I have scoured the change log looking for a possible explanation but I cannot find any potential culprits. The best way I can explain the problem is with these two short videos:

Working 5.0 UI


Broken 5.1 UI


I have rows of "action buttons" that are made up of various Unity UI elements, but they...

Inexplicable UI flickering in 5.1.0f3