[GAMEPLAY] Skill level-up prompt not disappearing

The arrow graphics that appear over the champion abilities won't ever disappear during some games. When you actually level up, the graphic will return to normal until you assign the skill point, and then return to the bugged state. I've encountered this twice, a few months ago on a Q-skill (can't remember the champ) and earlier today as Amumu on R. I don't know if exiting and reentering the game will fix it, but nothing I did within the game itself did anything to change it. I think I've only experienced this in the Howling Abyss, but I am not entirely sure whether the first occasion was SR or not. I have no idea what causes the bug, as it obviously doesn't happen too often, and thus I don't know how to reproduce it, or if it's possible to prompt by will at all.