Shield tunneling machines depend on reliable liquid-level feedback to control slurry, grease, and hydraulic systems. A rod-type magnetostrictive level gauge offers high accuracy and durability, yet harsh site conditions can still produce faults. Typical symptoms include a frozen display, fluctuating current output, zero drift, wrong high/low alarms, and intermittent communication errors. Common causes are a stuck or worn float, a dirty or bent guide rod, waveguide damage, loose terminal connections, moisture ingress, power-supply instability, and electromagnetic interference from inverters or power cables. To diagnose the problem, isolate the gauge and confirm supply voltage. Inspect terminals for corrosion and tightness, clean the rod with a compatible solvent, and verify free float movement. Compare the gauge reading with a manual dip measurement. Use a calibrated simulator and multimeter to test the signal loop and electronics. Replace worn seals, cracked housings, damaged probes, or faulty floats promptly. For prevention, schedule regular cleaning and calibration, protect cable glands from water, separate signal cables from power lines, check grounding, and add vibration damping where necessary. Prompt troubleshooting reduces shield tunneling downtime, extends sensor life, and improves operational safety. Record test results, replace suspect components, secure all covers before restart, and confirm stable output under normal tunneling load for at least one working cycle.