Assistance Needed:Issue with FMC125 and IridiumEdge Backup CommunicatI

Dear Team,

We are encountering an issue with our Teltonika FMC125 tracker integrated with an Iridium Edge modem for satellite backup communication. The FMC125 operates perfectly on GPRS; however, when the GSM signal is lost (SIM card removed), the failover to Iridium does not function as expected. Below are the details of our setup:

Firmware and Software Versions:
FMC125 Firmware: Version 03.29.00.Rev.720
Platform Used: Traccar V6.5

Wiring:
Iridium Pin 4Tx (Yellow) → FMC125 Pin 3 Rx(Grey)
Iridium Pin 3 Rx(Green) → FMC125 Pin 4 Tx(Green/White)
Iridium Pin 5 Pwr(Pink) → Equipment Power (12/24V)
Iridium Pin 2 Grd(Brown) → Equipment Ground
Iridium Pin 8 (Red): Outputs 6V during testing but not cabled
Note: The Iridium antenna is installed on the roof of the machine with an entirely unobstructed sky view

Configuration Details:
Iridium Services provider: Configured to send messages to the correct server IP and port. (same IP and Port configured in teltonika)
Settings in Teltonika Configurator:
GPRS Tab: Correct IP and port configured.
RS232 Tab: RS232 mode activated; “Backup Satellite” selected.
Features Tab: SBD configured to send satellite data every 1 minute (for testing).
I/O Tab: GSM signal loss set to “Panic”; other inputs/outputs set to “Low.”

Logs Analysis:

Log File 1:
Iridium Communication:
Signal quality checks succeed (CSQ received: 5), but errors like timeout(10) occur during SBD operations.
Data packets are queued but not sent.
GSM Communication:
GSM signal loss is detected (NO GSM SERVICE), but no successful failover to Iridium occurs.
Errors:
Frequent SIM failure messages and modem readiness issues (Modem not ready. Skip) may be impacting the GSM-to-Iridium transition.

Log File 2:
Iridium Communication:
The Iridium modem remains active during GSM loss, but errors like Unknown unsolicited msg AT+SBDD0 and timeout(10) persist during data transmission.
SBD packets are generated but fail to transmit successfully.
GSM Communication:
GSM signal loss is detected, but the transition to satellite communication is incomplete.
Summary of the Issue:
When the GSM signal is lost (SIM card removed to simulate network loss), the FMC125 does not switch to satellite communication via the Iridium Edge modem. While the Iridium module remains active and SBD packets are generated, they are not transmitted successfully.

The recurring errors (timeout, SIM failure) and logs suggest a potential configuration or firmware issue.

We have attached two log files for your review:

[Log File 1]
[Log File 2]

We would greatly appreciate your help in identifying the root cause of this issue and providing a solution. If additional details or further tests are required, please do not hesitate to let us know.

Thank you for your support.