Latest update of my case:
5 Starhub personnel came down to my residence to do the "joint inspection". 2 hub troopers and 3 network guys.
They opened up my Dlink RG and after connecting their netbook to some internal connector inside the RG, started a packet sniffer(Wireshark i think) to log my internet traffic and capture the issue's technical details.
They stayed ard half an hour to try waiting and see if the issue occurred again. It didnt(the issue happens almost entirely at night), so they left the wireshark equipment at my place and left. They asked me to note the next time it happen again and tell them the exact time so they can access Wireshark remotely and see the details.
I reminded them yet again about my deadline on 18th April, and they understood fully.
PS: I know about packet sniffers, so I'll probably NOT be accessing any secure stuff today