Garen and the Nexus

Garen's Q, Decisive Strike, is a basic attack modifier that deals increased damage and silences the target. When used on champions, minions, neutral monsters, turrets, or inhibitors, everything seems as it should be. However, when used on the Nexus, it seems to have reduced range as, more often than not, after activating Decisive Strike and targeting the Nexus, Garen will run up to it and just kind of stand there or attempt to run back and forth through minions, attempting to get into range. I've found that one of the places Garen can always seem to hit is on the fountain-side corner (bottom-left for blue side, top-right for purple side). When normally basic attacking, Garen's range is as expected and one minion isn't enough to body-block; he can whale on it all he wants. So, activating Decisive Strike should keep the the same range. However, it does not for some reason and one minion becomes enough to body-block and Garen may only be able to get the hit in on certain areas of the Nexus. Unfortunately, seeing as if I'm beating on the Nexus, the game is almost done, I haven't been able to test this extensively to find the other easy-hit zones. It seems the "corners" (it's a circle, I know, but the NE, SE, SW, and NW most areas) are the places he can hit the easiest, though I'm not entirely sure.