Issue like this already happen many years if you have subscribe anything that is less than 8 or 10Mbps, you will experience "deliberate" intermittent lost signal.
I also suspect, this must be deliberately-indirectly to make you to upgrade your existing plan tactics.
When you make a call to their support, you MUST wait approximately 20mins (if lucky) or even longer (if suay) and with voice auto attendant advise you to drop email on the problem you have, this is stupid when you dont even have the internet connection.
Waiting time really pain in the ass.
Reason given by Singtel Customer support, your Microfilter need to change etc...etc...
Once solved, either few days later or 1 week after, same issue occur again.
I've given up with singtel and switch to Starhub until then. No issue with starhub except their maintenance schedule distruption only.