TRB500 5G completely unusable - A08 modem firmware is broken, no support available

Networking Solutions
1

I’m extremely frustrated with my TRB500 and the complete lack of support from Teltonika.

The Problem:

My TRB500 cannot maintain a stable 5G connection. Every time the modem connects to 5G, it gets rejected by the network with these errors:

  • 5GMM reject cause => N1 mode not allowed

  • EMM reject cause => IMSI unknown in HSS

After the 5G rejection, the modem falls back to LTE but the data path is completely broken - ping times go from 20ms to 2000-10000ms or the connection drops entirely. The only fix is to constantly restart the interface.

I’ve been forced to completely disable 5G (nr5g_disable_mode=1) just to have a usable internet connection. I paid for a 5G router that I can only use on 4G.

My Setup:

  • TRB500

  • Router Firmware: 07.18.3 (just updated, didn’t help)

  • Modem Firmware: RG501QEUAAR12A08M4G_04.200.04.200

  • Carrier: yallo/Sunrise (Switzerland)

  • The SIM works fine in other devices

What I’ve Tried:

  • Updated router firmware from 07.17.5 to 07.18.3 - no improvement

  • Multiple modem resets, full router reboots

  • Different antenna positions

  • LTE-only mode (only thing that works)

The Real Issue:

The modem firmware A08 is clearly buggy. I’ve seen posts here saying A11 fixes 5G issues and the “5Ghoul” security vulnerability. But:

  1. Web UI says “Modem updates from the server are not supported for this device”

  2. The firmware is not publicly available anywhere

  3. There’s no direct support email - only “VIP Helpdesk” and forums

So we’re stuck with broken firmware, no way to update it, and no way to get proper support.

Questions for Teltonika:

  1. Why is known-buggy firmware still shipping on devices?

  2. Why is modem firmware not available through normal update channels?

  3. Why do customers have to beg on forums for firmware files that should be automatic updates?

  4. When will A11 (or newer) be made available to all TRB500 users?

I’ve spent hours today trying to diagnose and fix this. The device is essentially a €400+ paperweight for 5G use.

Anyone else experiencing this? Any Teltonika staff actually monitoring these forums?

3

OK i fixed it my self

1 Like
4

Greetings, @gt-solutions ,

Welcome to Teltonika Community!

Thank you for sharing the solution as it might be useful to other community members. In case you have any additional questions, don’t hesitate to let me know.

Warm regards,
V.

5

@Vilius, please don’t take me wrong, but I must say I found your answer not addressing any of the concerns @gt-solutions expressed. Further, is it the official Teltonika advice to follow the guidelines posted by an external party on GitHub? I cannot think so.

If those instructions are correct, why not post those instructions yourself (i.e. Teltonika)?

I don’t know how many threads I’ve seen with questions about the modem firmware version and how it can be updated. A forum search for “modem firmware”, today, gives 358 results.

Obviously, I haven’t read all of them, but I remember seeing seemingly conflicting messages from Teltonika moderators. Often with the reponse to stay clear of updating if there’s no clear issue, and that incorrect updating can damage the device (see, for instance, the response by Justinas on 21 November 2025 in TRB501 modem firmware update - #5 by Justinas ). @Vidas.K gave quite informative answes on the “how to” question.

The above mostly covers the “how to” … but questions regarding modem firmware version releases is mostly unanswered. Please prove me wrong.

I would recommend that Teltonika clearly communicates the policy on modem firmware releases, information on how to get and install the update, etc … and then refer to that in posts about modem firmware updating.

6

I’m the external party that posted that on github btw. i took me hours. But i thought ill let the world know. The connection is now super stable. I also think that this should come from the manufacturer.

1 Like
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