Pairing issue | 0x3D MIC failure error

[SK]

Hello everyone, 

I am using nrf52832 module with SDK v14.2 and SD v5.0.0 for my development.

Recently, i started facing the below issue: 

Once i try to pair the module with the smartphone ( in this case, samsung), its paired fine. Problem happens once i disconnect and try to connect again. Once i try to connect back, it gets disconnected throwing  error --> BLE_HCI_CONN_TERMINATED_DUE_TO_MIC_FAILURE.

I understand that somewhere message was not decrypted correctly but my question is, why now? It has not happened before in the few months we have been developing. Suddenly this issue came up. 

I tried erasing the module and loading the SD and app again but it still has the same issue. With my older version of the FW, it is throwing issues now.

Attached is the nRF sniffer log from Wireshark that i captured 

Could you guys tell me what can be the cause here? Why will it happen all of a sudden? What can be done to ensure this never happens? 

Thank you! 

Best Regards,

SK

[Sigurd]

Hi,

BLE_HCI_CONN_TERMINATED_DUE_TO_MIC_FAILURE could indicate that you are using incorrect encryption keys when you try to encrypt the link with a bonded device. Maybe the bonds were accidentally deleted on the phone. Try to remove the bond on both the phone and the nRF, and bond again. 

[SK]

Also, if this works, it still looks like a temporary solution. What if it happens in the future when the products are out with customers? How to eradicate this permanently?