Bearer continously disconnects after encountering Network reject

[Pradeep Gopanapalli]

Hi,

We are currently experiencing issues with the Telit FN990A28 module on
certain carriers, particularly T-Mobile. The modem disconnects every 30-40
minutes intermittently, and this flapping sometimes persists for days.

The only way to recover is by resetting the modem or rebooting the device.

The issue seems to arise when the network rejects the modem with the cause
"UE identity not derived by the network." Once this occurs, the bearer
continues to disconnect every 10 to 40 minutes. However, if the modem does
not receive a network rejection, the connection remains stable for days.

I’ve already checked signal strength, coverage, and bands, and I couldn’t
identify any issues.

I also checked the latest ModemManager repositories for any potential fixes
in this area, but I couldn’t find any.

Below is the log for the first network reject that causes the bearer to
disconnect: ( I am attaching full debug with this email, check for
2024-09-13T15:09:08.733
timestamp for first network reject)

2024-09-13T15:09:08.733 DEBUG daemon ModemManager[9721]:
[/dev/cdc-wdm0] Received message...
2024-09-13T15:09:08.764 WARNING daemon ModemManager[9721]: [modem0]
network reject indication received
2024-09-13T15:09:08.764 WARNING daemon ModemManager[9721]: [modem0]
service domain: ps
2024-09-13T15:09:08.764 WARNING daemon ModemManager[9721]: [modem0]
radio interface: lte
2024-09-13T15:09:08.764 WARNING daemon ModemManager[9721]: [modem0]
reject cause: ue-identity-not-derived-by-network
2024-09-13T15:09:08.764 WARNING daemon ModemManager[9721]: [modem0] mcc: 311
2024-09-13T15:09:08.764 WARNING daemon ModemManager[9721]: [modem0] mnc: 480

Package Versions Used:

   - *libmbim*: 1.24.8-2
   - *libqmi*: 1.28.6-3
   - *modemmanager*: 1.16.6-3

I would appreciate any advice or suggestions you might have on how to
resolve this issue.


Thanks,

Pradeep G

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