How can i speak with a Rioter about a very important bug that's afflicting a lot of people?

A couple of days ago i noticed this bug very often at the end of my games. The game basically bugs and does not give you a grade or mastery points, so if you need the weekly chest on a champion, do a game with it, you end up 15/0/10, you will not get a grade and you will not get the chest. I opened a thread on the LoL facebook page of my country and really a lot of people told me "Yeah this happened to me too". Today it happened to me 5 games in a row. It's really annoying especially if u're trying to get a champion to mastery 7 and need at least an S to get the token. How can i report this to a rioter?
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We're testing a new feature that gives the option to view discussion comments in chronological order. Some testers have pointed out situations in which they feel a linear view could be helpful, so we'd like see how you guys make use of it.

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