Can not mute

I can not mute the last player in the player list when i press TAB. This happens only on the last player in my team(not the enemy team). When I say last player I mean the player who's name and champion and kills and assists and creep score are all the way down. This can be fixed by changing the player order and putting the last player somewhere else (for example: the first player in the list/the top player in the list). But when I do that I cant mute that person. This happens every time i try to mute that person since the last patch. I expect a reward for pointing out this bug. Weather its an IP reward RP reward or whatever. I just expect a reward in some way.