Fountain/Tower targeting is messed up big time...

in a game of aram, we where pushed back to our 2 towers/nexus and i was running to fountain for safety from a jarven that was after me, so i get well in fountain atk range for it to atk jarven but it doesnt he sits their and destroys/kills me for a while with no fountain atk ......just after he kills me and has a chance to run away it then starts shooting him...... so he was in fountain range cause it shot him eventually but why didnt it before...

then towers shooting minions when enemy champs atking heros under them or atks wrong champions who are atking or they run in range and it doesnt shoot them or takes forever to shoot . plus is does laughable dmg too XD