Couple Level always rollback...

I noticed this since the anniversary start. My couple level reached level 21 already. but when i log out my couple level down to level 17. I don't know why. Please check or traced my inputted message on the system that i reached already the couple level to 21.Sorry i dont have any picture on couple level 21 because i dont have any idea that this is gonna happened and its a waste of time if I start again. please fix this. I'm new to this server. sorry for my English. thank you if you fix this fast mazey.

In-game name: Deiji
My Couple name is: lVANSl