OPCif you have the deep sleep then you just have the front led notification only , no logo notification , after open the whatsapp then the logo notification was blink.
This is not a bug. Front led is regulated in Notification settings
The back logo notification light is regulated in Armoury Crate, Console, System lighting, Advanced settings, Notifications
So you can choose to have the notification light front, back or both. Really nice solution.