Green LEDs are usually a sign of a healthy modem, maybe some disruptive work is being undertaken in your suburb's NBN Network. Suggest to have a look at your firmware version in case it is trying to update itself and then do a Factory Reset using a paperclip into the Reset hole with the modem powered on. It will clean out all settings and refresh itself. If situation doesn't improve, contact Optus and have them remotely test the network connection and the modem. It may have become faulty.