Brrrr … I do have a RUTC50 and updated the modem yesterday to RG520NEBDCR03A05M4G and have the same issues with 5G now:
4277 Wed Apr 8 13:50:01 2026 kern.crit kernel: [24557.129964] qmi_wwan 2-1.1:1.4 wwan0: NETDEV WATCHDOG: CPU: 0: transmit queue 0 timed out 5230 ms
4278 Wed Apr 8 13:50:02 2026 daemon.notice netifd: mob1s2a1 (3745): Request timed out
4279 Wed Apr 8 13:50:06 2026 kern.crit kernel: [24562.139946] qmi_wwan 2-1.1:1.4 wwan0: NETDEV WATCHDOG: CPU: 0: transmit queue 0 timed out 5010 ms
4280 Wed Apr 8 13:50:06 2026 daemon.notice netifd: mob1s2a1 (3745): Request timed out
4281 Wed Apr 8 13:50:10 2026 daemon.notice netifd: mob1s2a1 (3745): Request timed out
4282 Wed Apr 8 13:50:11 2026 kern.crit kernel: [24567.149948] qmi_wwan 2-1.1:1.4 wwan0: NETDEV WATCHDOG: CPU: 0: transmit queue 0 timed out 5010 ms
4283 Wed Apr 8 13:50:14 2026 daemon.notice netifd: mob1s2a1 (3745): Request timed out
4284 Wed Apr 8 13:50:16 2026 kern.crit kernel: [24572.169944] qmi_wwan 2-1.1:1.4 wwan0: NETDEV WATCHDOG: CPU: 0: transmit queue 0 timed out 5020 ms
4285 Wed Apr 8 13:50:21 2026 kern.crit kernel: [24577.179945] qmi_wwan 2-1.1:1.4 wwan0: NETDEV WATCHDOG: CPU: 0: transmit queue 0 timed out 5010 ms
4286 Wed Apr 8 13:50:26 2026 kern.crit kernel: [24582.189979] qmi_wwan 2-1.1:1.4 wwan0: NETDEV WATCHDOG: CPU: 0: transmit queue 0 timed out 5010 ms
4287 Wed Apr 8 13:50:31 2026 kern.crit kernel: [24587.199946] qmi_wwan 2-1.1:1.4 wwan0: NETDEV WATCHDOG: CPU: 0: transmit queue 0 timed out 5010 ms
4288 Wed Apr 8 13:50:36 2026 kern.crit kernel: [24592.209947] qmi_wwan 2-1.1:1.4 wwan0: NETDEV WATCHDOG: CPU: 0: transmit queue 0 timed out 5010 ms
4289 Wed Apr 8 13:50:37 2026 daemon.notice netifd: mob1s2a1 (3745): Request timed out
4290 Wed Apr 8 13:50:38 2026 user.notice mobile.sh: Received unknown error(1/5): "Unknown error"
4291 Wed Apr 8 13:50:38 2026 daemon.notice netifd: mob1s2a1 (3745): Mobile connection lost! status: Unknown error
4292 Wed Apr 8 13:50:38 2026 daemon.notice netifd: Interface 'mob1s2a1' has lost the connection
4293 Wed Apr 8 13:50:38 2026 daemon.notice netifd: Network device 'wwan0' link is down
4294 Wed Apr 8 13:50:38 2026 daemon.notice netifd: mob1s2a1 (6650): Stopping network mob1s2a1
4295 Wed Apr 8 13:50:38 2026 daemon.notice netifd: Interface 'mob1s2a1_6' is now down
4296 Wed Apr 8 13:50:38 2026 daemon.notice netifd: Interface 'mob1s2a1_6' has link connectivity loss
This happens every 30-60min. My 5G provider(s) are all NSA.
So, I would say, something is terribly wrong with the modem firmware RG520NEBDCR03A05M4G.
Teltonika, please fix this by providing an official way forward! Firmware RG520NEBDCR03A05M4G basically breaks the core functionality of that router…