There have been two people in the Discord today Jan 25, after the 10.0.5 patch, saying that they get no completion credit for battles in Dragonflight for the Family achievement, and I see this post on the US Bug Report forum
I can’t test it myself, since I already finished the achievement.
If you are affected by this, make a Bug Report in the in-game Support option. You can also add a post here if you are EU and are affected, or have more information.
According to a note by DragonsAfterDark on Xu-Fu’s, the problem is that the win credit is cached,
Currently, to receive credit you’ll need to log out then back in. I believe it caches the wins, meaning you can do multiple and it should still count once you log out and back in. Hopefully they fix this soon. ^^’