There is a possibility TM has severely oversold the bandwidth allotted to your respective areas. At night when more people are at home, everyone gets online, and when they're up and out of the house during the day, u get more bandwidth to use. Keep printscreen copies of your speedtest results with time and date for each test, and keep on complaining.

Is everyone getting that problem on Wi-Fi 5Ghz?

I changed my bandwidth setting in my Unifi D-link router and it solved the slow problem.

are you on a high-rise or landed property? which service do you usually download from? using a vpn?

i’ve been getting a consistent 800 mbps all the time. my old router (wdr4300) technically supported gigabit speeds, but it would occasionally drop to 100 mbps, so i got into the habit of checking my speed every time i booted up my pc.

since i replaced the router, i haven’t experienced any speed drops. actually, ever since i moved in, i’ve had full speed all the way. started with 300 mbps, then got a free upgrade to 500 mbps, and now 800 mbps. always maxed out, no issues.

that being said, i never trusted their router. i've been using my own since day one.

Landed  mine drop to 0 mbps  when midnight , what model router u using can intro

when i signed up tm gave me d-link wbr-2300. i still have the box, lol. if i remember correctly, they only started giving out wdr4300 much later.