I am not able to ssh to raspberry pi after 2-3 hours. This all started after installing Plex Server on it but not sure if this is a mere conincidence. At first, I got "connection reset by peer" error after typing "ssh user@ip" on the terminal. Assuming, it was a server load problem (hence crashing), I swapped my sdcard from raspberry pi 2 model b+ to raspberry pi 3 after update/upgrade. Now I get "Connection closed by port 22" when i tried to ssh. Tried many computers. All the other non ssh connections also don't work. After every restart it works normally for a few hours. I can successfully ping but can't connect. How I start to debug this issue? Where to look for trouble? How to see server logs? I am running latest version of Raspbian on it. Pi is powered through usb hub. It is connected to wireless network. I wasn't able to ping with raspberry pi 2 model b+ version but after swapping cards to raspberry pi 3, ping works when SSH fails. There is no firewall. It had been working fine with this kinda setup for months. I understand there is some non trivial issue and wondering how to check server logs for trouble. Please advise.