Hands of guldan deck. Played game. Logged out. Logged in later. Deck showing 24 of 30 cards. Deleted deck. Recreated off recipe. Played games. Logged out. Logged in a few hours later. Deck showing 24 of 30 cards. I rarely play warlock so not sure how long has happened. I did level up today. All from my ipad. Have not checked other.
It happens to me too. It has nothing to do with warlock or leveling up.
How many legendaries are in your deck?
Also, I’m having this on PC.