Question about Flex Queue

Hi, I have a question, for my flex promos i won 8 out of 10 games. When i got to play my 9th and 10th placement games it matched me with diamonds and plats and i'm only gold 4. For my 1st-8th placement games i had good performance and was getting match with players my elo. I'm just a little confused why this is happening and what to do. any thoughts?

Here are some pics of the matchups

1. https://gyazo.com/5ac87d940351582052bc44aab519e78c

2. https://gyazo.com/dce274e683aa4b9dbc7c4a74d9628ef3

3. https://gyazo.com/e469a4d88010e103dfdf835538a970ee

4. https://gyazo.com/25c884fc5479c5cbf74c953a031a4277

oh and here's a weird fizz glitch that happened in my game lol

• https://gyazo.com/22751042864e99c4c28d4598683cbe9b