1.Uninstal WhatsAppHI all.
I have Mi5 gemini, and I still have double notification sound in whatsapp. It was fixed?
2.Delete from phone WhatsApp folder. ( IMPORTANT !! )
3.Instal WhatsApp from Play Store.
Works in my mi5
No more double notification sound, and i'm HAPPY
PS.
( I noticed that after deleting the WhatsApp folder and reinstalling it, the folder that was created contains completely different directories than before the deletion. Most importantly, notifications are not duplicated. )