Switch overloading causes net problem

Hello all.

From time to time in random periods I face the following problem.

Suddently all network devices in LAN (servers, routers)stop responding. I ping them and I get something like this:

Reply from 192.168.x.x bytes=32 time=230 TTL=64
Reply from 192.168.x.x bytes=32 time=30 TTL=64
Reply from 192.168.x.x bytes=32 time=120 TTL=64
Reply from 192.168.x.x bytes=32 time=50 TTL=64
Request Time out
Request Time out
Reply from 192.168.x.x bytes=32 time=12 TTL=64
Reply from 192.168.x.x bytes=32 time=59 TTL=64
Request Time out
Request Time out

This symptom appears to all devices that are installed in the LAN.

In order to resolve this problem I begun switching off the switches one by one in order to isolate the problem. I finally determined the switch that if I switch off then the problem is resolved.

I replaced this switch 15 days ago but now the problem occured again. I switched it off again and the problem was resolved so I concluded that it is not a switch problem. The switch becomes overloaded for some reason.

This problem occures randomly 2-3 times per month.

Do you know what might be the cause of the problem?

Thank you in advance.

Stergios