Have you tried another modem?
Have you tried to factory reset and re-setup the S@GEMCOM to make sure its not faulty?
If you've done this and its still the "WiFi" dropping out, then you need to ask Optus to consider replacing it, assuming its still in warranty.
I tried changing the modem the last time I had this problem.. it never did anything. I'm not doing it again as I don't want to have to stuff around changing passwords for everything connected to it.
If it were the modem, the technician would've told me to replace it when he came here. He said according to the light patterns, that it is a NETWORK issue. And I trust his opinion WAY more than the useless foreign idiots that keep wanting to "test the line" ..
This absolutely sounds the same as my issues.
I posted another query almost identical in symptoms as yours just a while ago.
I am wondering if it could be a software issue on the modem itself?
The problem here is, a "NETWORK ISSUE" (ie: within the Optus network) does not cause "WiFi" issues, so whomever told you that your WiFi light flickering is caused by an Optus network problem, has unfortunately been disingenuous towards to you.
The fact you said "You tried" another modem and the problem continued, makes me ask the following question:
Are you connecting to the WiFi provided by the S@GEMCOM or something else? Because replacing the DSL modem (Which is inside the S@GEMCOM would most likely clear up the fault).
This won't help with your connection issues, but I can confirm how frustrating Optus actually is. I had a tree branch take my phone and internet down and although it was physically broken, they (the support staff overseas) were insistent that they run line tests to test the connection. I continually told them that the line is physically broken and I can send them a photo of me holding the broken end of the line if they like and I was told that they had to go through protocols. I experienced the same problem of being disconnected and going through the same explanation each time. Anyway, a Telstra technician came and reconnected the line 4 days later and it worked for 2 weeks and now it's out again. Our internet speed has been poor for many years and I might have to bite the bullet too and go with Telstra at a higher price but hopefully better service.