R7000 packet loss?

部R7000而幾日唔知做咩突然好多packet loss
情況係ping ISP既gateway冇事
ping google/youtube等大約10~50%不等loss
跑speed test慢到得番0.1Mbps(本身200)

試過upgrade/downloadgrade firmware(都係原廠既)
Reset factory default
reboot GPON機

直接ping 192.168.1.1 冇事,加上全有線,唔似係LAN部份出事
加上telnet入router再ping出去更加證實唔關LAN事

ISP: Netvigator
Router: R7000
FW: V1.0.4.28_1.1.64
QoS off