[GAMEPLAY] Minion ignores targets, only attacks enemy minions in respective enemy wave

While playing in bot lane, a red melee minion ignored all other potential targets and walked to the middle of lane.

The two waves were fighting at the enemy team's (purple team's) outer tower, and my champion was behind them, outside tower range, last hitting. The next wave of enemy minions arrived at the outer tower but a red melee minion walked around all valid targets, ignoring the enemy minions, ignoring my champion, who was a valid target to lock-on to the entire time and walked to the middle of bot lane. He only moved toward and/or attacked minions in the respective blue team wave. Seeing this, I looked at the match clock which read about 7:10, so this minion should have belonged to wave 11.