i have had tpg come out to my place 2 times and a telstra tech (on behald of tpg) and no1 knows why my connection drops out. I have replaced my modem (one of the lan ports failed), replaced the filter and phone cable from the phone to the filter and the modem & i still get drop outs. i now just restart the modem from my mobile if i cbf'ed getting up & live with it.
factory resetting, firmware updates, iso test haven't fixed anything in my case. However i would advise you to atleast try it before calling tpg