Same. Went from archon 3 to guardian 3. Lost 7/10 calibration games playing support. Just won 10/10 subsequent games carrying. I didn't care because even though I dropped a lot of MMR, I don't think it's crazy I fell back.
Also, winning my games like this helps me validate I've improved as a player (I climbed from herald to Archon then dropped back to guardian). The other thing, those games I lost were all shutouts, like 0-12 at 10 minutes which is very unusual. In most cases, feeding was from over aggression in the laning stages.
I had a positive KDA in all games as a support and in some games the highest hero damage on my team by far so I didn't feel bad about my performance as a whole.
If you aren't guardian MMR you'll climb fast, which is what I'm experiencing right now. But it sucks, I feel that.