Garen - Decisive Strike Doesn't Decisively Strike the Nexus [GAMEPLAY]

When attacking the enemy nexus, Garen's Decisive Strike delays when activating it to get the auto-attack reset. I have had delays that last as long as Decisive Strike is still active (~5 seconds). However, usually this delay is about 1 second. This happens anytime I use Decisive Strike to hit the nexus (and has been happening for a long time now). I typically only get ahold of Garen on Howling Abyss, so it's possible that the problem is localized to that map. I have not tested to see if this bug is present on any other maps. Please fix. Thanks!