Nordic not responding to LL_FEATURE_REQ from central

[DrewW]

We are seeing an issue with Android 13 on Samsung phones connecting to our device over BLE. After CONNECT_IND the phone will attempt to send a LL_FEATURE_REQ. It takes about 6 attempts before it is ACK'ed by the Nordic. Once the Nordic ACK's, it does NOT respond with LL_FEATURE_RSP. In the images below I attempt to connect twice, both fail. The detailed image only shows the time around when one the LL_FEATURE_RSP is received by the Nordic and then there is no response. This process is successful with the same Nordic/FW but with different phones. On other phones the first packets are typically a LL_VERSION_IND exchange. 

Parts: 832 / 840

Soft Device : 6.2.2 

[Kenneth]

Hello,

Can you share the sniffer log? Is this frontline?

Kenneth

[DrewW]

Hey Kenneth, 

I am using frontline. Thanks for taking a look at this.

failed_connections.zip

Drew

[Kenneth]

Hi again,

Looking at two places where the phone try to initiate connection:

In both cases it looks as simply the connection request packet was not received (or ignored) by device (e.g. either due to noise prevent the packet from being received and/or that the device have whitelist enabled), in which case it will simply continue to advertise as normal. I can't see that the device ACK the communication here?

Best regards,
Kenneth