AS-604T is killing my network/internet (Yellow Triangle)

[mgcan]

I have Dlink 868L router and 2 Windows PC, NAS, Android TV are wired connected.

I have AS-604T NAS since 2014 and has been working fine. But for last 3-4 month it is behaving weird. It is on auto power-off and power-on mode.
• Power off at 2am at night
• Power on at 5pm

Each time it is turn off at 2am, it kills the internet and whole network connection (Yellow triangle on Windows PC). In the morning when I get up, there is no internet (wired and wireless).

Each time it turn on at 5pm, it kills the internet and whole network connection (Yellow triangle on Windows PC).

When I try to switch off and switch on manually, then also it kills the internet/network.

To get back the internet, I need to power cycle the router.

I tried using port Lan2 and also changed the cat5e, without any success.

On further trouble shooting, I notice that if I pull out and insert back the TV ethernet cable, the connection comes back.

Please help me if fixing this issue.