USG FLEX 200H: LAN port is experiencing unstable up/down status.

I have a USG FLEX 200H and a WAC500, both managed via Nebula Control Center (NCC)

• Organization Name: Tony House
• Site Name: Tony House
• Firmware Versions:
  • Gateway (USG FLEX 200H): 1.32(ABWV.0)
  • Access Point (WAC500): V6.70(ABVS.6)

Network Topology:
Internet — [public IP] — USG FLEX 200H — [Port 5] — WAC500

Issue:
Port 5 on the USG FLEX 200H is continuously flapping (going up and down). Please refer to the attached screenshot for details.

The Ethernet cable between the gateway and access point has been checked and confirmed to be in good condition.

Please help investigate this issue and let me know if you need any additional information.

Thank you.

Quang