Disconnection (freezing)

hi everyone

I use my cloud 4t for like 4 years and suddenly it begins to disconnect from the network after 15 to 20 minutes it will not work again unless I unplug the power
it seems to me it freezes because after the disconnection I unplug the ethernet cable, the front led is solid blue instead of solid red and back light is solid yellow instead of no light (activity back led is off)

I have the latest firmware and reset it many times and I did reserved static IP for it from the router
cloud access is off
standby is off

any idea how to fix
any comments may help me

Is this a 1st or 2nd generation My Cloud? Firmware for 1st generation is 04.xx.xx, 2nd generation is 02.xx.xx. For the correct User Manual use this link. Look at LEDs.

https://support-en.wd.com/app/products/product-detail/p/126

Has anything changed on your local network recently? Like changing broadband providers, changing network routers (or adding a second one), adding a new network device?

One troubleshooting suggestion, if you haven’t already done so, is to access your local network router and assign/reserve an IP address for the My Cloud.

Other troubleshooting suggestions, try putting a network switch between the My Cloud and the router to see if the problem resolves itself. In certain instances there is a bug between some broadband routers and the My Cloud.

My Cloud is not recognized when connected to AT&T Uverse, Pace, Arris, Ubee or Sonic Gateway Routers
https://support-en.wd.com/app/answers/detail/a_id/3637

It is the second generation

I saw the leds in the manual it is helpful but
It seems everything works fine in the first 15-20 minutes after that its freezing and should be turned off And on again

I have already reserved ip for it
But you are right I have changed the router to a new one
I used another switch between the router and mycloud as you said but nothing changed