More than one Push notifications comes to the same iOS device even active device's device_token is different

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Here is our scenario,

1. get the 'deivice_token' each time when user register to our app.
2. send push notifications from back-end server to the registered 'device_token'

What happen :

   Our test case : Our app allows multiple registrations  (Same user can register more than one time)

• Register new user -> "assume the device_token is device_token_1 and email is test@icloud.com".
• Uninstall the app or, logout and register same user again. now the device token is difference -> "assume the device_token is device_token_2 and email is test@icloud.com".
• Now the active device's device_token is device_token_2.
• from back-end we send push notifications  to the user using email. in here to test@icloud.com (two device_tokens for the same user and only one is active).
• Even active  device_token is not the device_token_1, two push notifications comes to the device. (for device_token_1  and device_token_2).

NOTE : same scenario with the Android working properly. it only gets the active token and send the push notification to that.

Hope your help with this.