Actually, there have been a lot of problems with turrets not focusing a champ damaging you under turret recently and the turret goes on attacking minions when its happening. There are videos of people getting hit at the base of their turret by a melee champ and the turret continues to attack minions. If it is extremely irritating or frustrating for you to play while this is going on, I suggest, if you have the option to, to not play rift until its fixed or go play another game. Or you could adjust your play-style to work around these problems and not even depend on the turret to help you. I know it's annoying, it frustrates me too, but until Rito notices it and works to fix it, adjusting the way we play is probably the only reasonable solution to a problem like this.