[GAMEPLAY] Aurelion Sol may not gain movement speed linearly on E passive

So, I'm not sure if this is strictly a display bug or if his movement speed is also affected. I repeatedly hovered over the Comet of Legend buff icon while gaining movement speed (E was at rank 3), and at one point the buff text said that the movement speed went 32% -> 25% -> 35%. I have GIFs that show this:

First GIF shows this at full speed (GIF looks bad unless you click on it): http://imgur.com/mgyct2W

Second GIF is a slice slowed down to 0.25x, clearly showing that the movement speed does not ramp up linearly: http://imgur.com/T7wl9hJ

I realize that the movement speed decays when Aurelion Sol turns, but this did not happen in this case. No movement speed commands were given (since I was hovering my cursor over the buff bar the entire time), and the autopathing didn't turn him, either.

EDIT: Did a test... Got this to happen on the very first try. Here's a 0.25x speed GIF where it says that the bonus movement speed briefly drops to 0% (E was at rank 1): http://imgur.com/Xwm8yWg

Repro isn't 100%, maybe 5%.