Hi,
I’m experiencing repeated modem crashes on a RUTX50 where the internal Quectel RG501Q-EU modem disconnects from the USB bus and re-enumerates up to 60 times per day. This results in short Internet outages and “Internal modem unavailable” messages in the Web UI. The router it self is very stable, only the modem part is experiencing issues.
I’ve done a bit of testing and logging, and the problem looks like a modem firmware crash or USB subsystem fault, not a signal or temperature issue.
Setup: RUTX50, Firmware RUTX_R_00.07.17.5, Modem firmware RG501QEUAAR12A11M4G
Placed in the Teltonika Outdoor LTE & 5G/Wifi/GPS Antenna For RUTX50
Summary of the Issue
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The modem goes offline between 4–60 times per day.
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Outages last from a few seconds up to a few minutes.
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During each event, the router reports “Internal modem unavailable.”
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The modem immediately re-enumerates over USB and reconnects.
Key Log Messages During Each Event
These lines appear consistently in system.log whenever the modem fails:
qmi_wwan 2-1:1.4 wwan0: unregister 'qmi_wwan'
usb 2-1: USB disconnect, device number XX
usb 2-1: device not accepting address, error -22
xhci-hcd: ERROR: unexpected setup address command completion code 0x11
ttyUSB0/1/2/3 disconnected
new SuperSpeed USB device found
qmi_wwan ... register 'qmi_wwan'
Monitoring Script Results
I created a script to track every modem USB reset. Example:
2025-11-28 06:23:58 - MODEM USB RESET DETECTED
SIGNAL: { "rsrp": -93, "rssi": -61, "sinr": 2 }
TEMP: { "temperature_value": 280 }
Tests I’ve done
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Disabled 5G → still happened
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LTE-only → still happened
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Locked modem to single band (B20 only) → this is the only mode that has been somewhat stable so far
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Disabled 3G/UMTS
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Modem temp is low (26–29°C during events)
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Using Teltonika outdoor 5G antenna enclosure (PoE powered)