Problem solved.

Pull the network cable from router to the notebook before browse to fb 😞

Cause of problem should be from server switching between and Donno what inside the packets that disrupted wifi connection. With network cable connection, once I reach the end of the page and press PgDn, the opera's status bar showed that it was connecting to that edge-chat, hesitated for a few seconds before proceed to load more data.

However, if pull cable out from notebook and use only wifi - connection drop instantanously when press PgDn to load more data.

Thank you again! @alobpreis , @joshi