RUTX50 internal modem unstable after RG520 modem firmware update – SIM failure, gsmctl N/A, no registration

Networking Solutions Issue
1

Hello,

I am experiencing a persistent internal modem problem on a RUTX50 which started immediately after a modem firmware update. Before the modem update the router was working normally.

The issue persists after factory reset, firmware downgrade and clean configuration.

Device information

Device: RUTX50
Hardware revision: 0404
Batch: 043
Manufacturing year: 2024

Router firmware tested:

RUTX_R_00.07.21.2
RUTX_R_00.07.20.3

Internal modem:

Quectel RG520N-EBDC

Current modem firmware:

RG520NEBDCR03A05M4G_A0.300.A0.300

SIM:

Telekom Germany (tested working in other devices)

Antennas:

4 cellular antennas connected

Problem description

After the modem firmware update the modem became unstable and mobile connectivity cannot be established reliably.

Typical symptoms:

gsmctl -I returns N/A
gsmctl -q returns N/A
Internal modem shows limited service
Data connection disconnected
mobifd and gsmd running but unable to retrieve modem info
Modem accessible via AT commands

Observed modem behavior

SIM initially detected:

AT+CPIN?
READY

RF sometimes visible:

AT+QENG=“servingcell” shows Telekom network
Example RSRP approx -92 dBm

However modem frequently reports:

+QNWINFO: No Service

After modem reset:

AT+CFUN=0
AT+CFUN=1

Sometimes results in:

+CME ERROR: SIM failure

After this event:
gsmctl stops working and modem state becomes inconsistent.

Kernel observations

Modem enumerates correctly:

ttyUSB0 – ttyUSB3 present
cdc-wdm0 present
wwan interface created

No permanent USB crash loop.

Previous logs included:

Write to modem failed errno 5
Failed to send command to modem
Failed to get SIM state
Request timed out errors

Troubleshooting already performed

Factory reset
Router firmware reinstall
Firmware downgrade test
Return to latest firmware
Modem CFUN resets
mobifd restart
gsmd restart
GPIO modem power reset
Direct AT diagnostics
SIM verified working
APN verified
Antennas verified
Different RAT preference tests

Issue persists.

Current behavior

Modem sometimes detects RF but fails registration and eventually reports SIM failure or becomes unavailable via gsmctl.

Since the problem started directly after modem firmware update this may indicate modem firmware corruption rather than configuration error.

Questions

Is RG520NEBDCR03A05M4G_A0.300.A0.300 the recommended modem firmware for RUTX50 with 07.21.x?

Is newer RG520 modem firmware available?

Is there a modem recovery or emergency flash procedure available?

Does SIM failure after CFUN indicate modem firmware corruption?

Would Teltonika recommend modem firmware recovery or device replacement?

I can provide additional logs if required.

Thank you.

1 Like
3

Hello, @Leigh ,

For troubleshooting purposes, we will require more sensitive information from your end, such as the troubleshoot file, which may contain passwords, public IP addresses, serial numbers, and such. To avoid leaking this information, we have sent you a form to fill out, which you will receive in your e-mail inbox that you have registered your account with in the forums. In the Ticket ID field of the form, please enter the ID of this thread, which is 18483.

Please let me know once you filled out the form.

Thank you,
V.

4

Hi Vilius,

i’ve just replied your form right now.

5

Greetings, @Leigh ,

I hope this message finds you well,

I have provided you with further instructions via email, could you please confirm if you received it?

Kind regards,
V.

6

Hi Vilius,

I just received the email yesterday in which you asked for a troubleshooting file.

I replied to it right away.

Bye, Leigh

7

Greetings, @Leigh ,

I hope this message finds you well,

I have not received the response with the troubleshoot file, could you please double-check if the email was sent?

Please let me know if you are facing any issues sending the file.

Best regards,
V.

8

Hi Vilius,

i’ve sent the file twice.
I have replied your Mail two times.

Monday and Yesterday.

So provide me an link where i can Upload the file directly.

Regards, Leigh

Checked the sent Folder of the email Provider and Both emails are sent.

9

Thank you for your swift response,

Since we did not receive any response, I sent you an email from a different mailbox, please check your inbox and let me know if you received it.

Kind regrads,
V.

10

Looks like the same issue here

here

and here

all of them got issues after a ModemUpdate.

11

Greetings @Vilius

any news? If not, can you provide a Firmware File/Downgrade Script to downgrade the Modem?
That will help until you find the issue.

kind regards,
Leigh

1 Like
12

Is there any news here?

Any possibility to downgrade the modem firmware?

13

Hello,

I hope you’re doing well,

I have forwarded the troubleshoot file to our R&D team for further investigation and I am still waiting for an update from them. I will inform you once I have more information on the matter.

For now your patience is very much appreciated.

Best regards,
V.

14

Hello,

I just wanted to provide a short update.

The device has now been unusable for mobile connectivity for more than two weeks. Since the issue started directly after the official modem firmware update and no workaround is currently available, today I have also started a replacement process with the reseller due to the downtime.

I am still very interested in a possible modem recovery firmware or downgrade option if available, as this could potentially resolve the issue faster.

If any additional logs or tests are required I can still provide them.

One additional question:

Since the issue started directly after the modem firmware update and the modem still responds to AT commands, could this indicate a corrupted modem NV or firmware state?

Is there any RG520 recovery procedure available (for example emergency modem firmware reflash or QFirehose recovery package) that could be tested before replacement?

I would be willing to test recovery firmware if available.

Thank you for your support.

1 Like
15

i have found a workarround for the problem:

https://community.teltonika.lt/t/rutm30-modem-problem-after-fw-update/18546/5?u=eat

16

@eat

Thanks for that hint, but won‘t work for me.

17

You select the right SIM Card for editing the connection Type?

18

Hello, @Leigh ,

I hope you’re doing well,

I have sent you an email with further instructions, could you please confirm that you received the email?

Best regards,
V.

19

Hi @Vilius

i did not get any email right now.

20

Hello,

Thank you for your swift response,

I have sent you an additional email from a different mailbox, could you please confirm if you have received an email with further instructions?

Kind regards,
V.

21

Hi Vilius,
I replied to the email and sent a troubleshooting file for the fourth time.
Nothing has changed on the router except the time and date.
Please provide a guide on how to downgrade the modem firmware.
I’ve had this expensive brick sitting here for three weeks now.
It’s frustrating.

1 Like