1. Check the faulty port. It is found that the port is set to an unloaded port.
2. Delete the original services and recreate services. The fault persists.
3. Perform a warm reset on the faulty N1PQ1 board. The fault persists.
4. Perform a cold reset on the faulty N1PQ1 board. The fault is rectified.
5. Query relevant version features. It is found that the modes of processing DOWN_E1_AIS alarms are different between R3 and R7.