Placement games not making sense

So I managed to fight my way to Gold V at the end of season. When the season ended I updated client and went through my placement games in the off season. Went 7/3, placed in Silver 1 and a handful of games later I was back in Gold V. Season 7 arrives, I have to redo my placements for solo queue. Go 7/3 again but am placed in Silver IV.

I won more games in the off season than lost, trying to understand how I dropped so much in a short amount of time. Is flex queue differently calculated to solo/duo?