Matchmaking Problem

So I main ADC.

I'm not saying I'm the best carry ADC or whatever, and I don't pretend to be Silver 4 and belong in the Plat 1. But I had a 65ish % win ratio as an ADC from Bronze 2 to Silver 4 after my Placement Matches. Trying to play ADC as much as possible I kept picking Bot and Mid in the Matchmaking process. It now has been 7 games in a row I get placed Mid and it frustrates me.

The point of Matchmaking was that you could play the roles that you want to play. I would be okay with playing 50-50 of mid and ADC but I've had a full week-end of Mid and this is a really hard problem for me to understand.

Riot needs to find a way to make sure you get your primary role at least 33-40% of the time, and not 1/8 games.