EMS reject error

[J_Dev]

Hi all,

I’m experiencing an intermittent issue with a Teltonika TRB245 where the device frequently disconnects from the mobile network and RMS platform. The system log shows the following recurring message:

Modem `1-1.4 [2c7c:0125]` URC Event: ESM reject cause => Missing or unknown APN

Here’s what I’ve confirmed so far:

• The APN is correct and has been manually set in the WebUI (Network > Mobile > General)
• The SIM is provisioned for data and works fine in other LTE equipment
• The device does sometimes successfully connect and receive an IP address (e.g., from AT+CGPADDR)
• However, after some time (or post-reboot), it throws the ESM reject error

I’ve noticed these patterns:

• USB modem (Quectel EC25/EG25) disconnects and reconnects intermittently (seen in dmesg)
• oom-killer messages in the logs — possibly causing service restarts
• Only PDP context #1 is active (+CGACT: 1,1) when it’s working — others are inactive

I’ve already tried:

• Forcing the APN via AT+CGDCONT=1,"IP","my_apn" in the custom AT command section
• Updating firmware to the latest TRB2 stable release
• Disabling unnecessary services (tcpdump, gpsd) to reduce memory usage

---

Questions:

1. Has anyone seen this “ESM reject cause => Missing or unknown APN” occur even with the correct APN configured?
2. Are there any known race conditions or modem timing issues after USB resets?
3. Is there a better way to force or persist the APN across modem reconnects?

Any help or insight would be appreciated! Happy to provide full logs or configuration if helpful.

Thanks,
J Dev

[Matas]

Hello,

I’ve sent you a form to fill out so we can continue our conversation in private, to avoid accidentally leaking any sensitive information. In the Ticket ID field, simply enter the thread’s number, which is 14796.

Thank you,
M.