Problem with old IJN DDs is back. WG decided to remove all battles played with old DDs (Mutsuki, Hatsuharu, Fubuki, Kagero) from API.
That decision broke data integrity - total battles count for account is no longer equal to sum of battles count per ships.
To maintain the accuracy of our statistics (win rate, PR etc) we decided to display all of our data without those missing ships.
The problem has been reported to WG Support, we are waiting for a response. You can check status of this and other API bugs here