I will try to find the old Optus modem, problem with that modem is so old (~2004) and basic that does not even have Wi-Fi.
I do not understand why my connection worked very well just after the fix, on Monday 10.
I measured a download speed of >10 Mbps.
Then last Thursday it started playing up again, it was fine after that (Friday and so on), then this morning again frequent drop outs.
Technician who came on the 10 adviced to change battery in my old wireless handset, that I did, I got a new battery and fit it.