Sorry I just checked its only my PC experiencing this issue.
My other devices like laptop and phone are on WIFI connection

PC is connected to ethernet port

Congratulations, you just narrow it down further

Check the LAN cable / port / PC driver

not issue unifi its you crap router if you reboot router to get solve after few hours will come back problem that mean crappy router due unable handle because cpu weak and ram weak that low spec

you need buy own router to get solve don't buy cheap
you 500mbps then take TP LINK AX73 enough

mine ASUS Router was paid RM8xx expensive its already too old 7 years still strong no issue 500Mbps i never reboot router
Uptime 27 days 20 hour(s) 35 minute(s) 23 seconds look near 30days i wont reboot
my router ASUS RT-AC68U already old but wifi 6 i always getting full speed wifi 500Mbps for 5Ghz

i suspect you crappy router issue

i had used crappy router for use PC always ethernet port LAN cable but few hours still slow and need reboot router back to normal after few hours come back problem to
so now i use my own asus router for use PC always ethernet port LAN Cable and tested never had problem always stable

Anyone having issue on Unifi in Klang area (Near HTAR) suddenly internet was sluggish now is totally off blinking LOS