When you have the F5 mode ON, below layer 60-61, I can see a graphical bug in the sky, I tested this on a Vanilla Server, but not in Singleplayer, above layer 60 there aren't any bugs of this type.
Environment
Windows 8.1, Java 1.7.0_51-b13, Radeon HD 7770 Graphics Card.
How high was your FOV?