Good news, and bad news. The good news is you can tell the household it isn't your fault for swapping the hub (in like for like circumstances not swapping it might have made things worse, whether they believe it or not), the bad news is that looking at the BQM I'm seeing a typical over-utilisation pattern, and perhaps a bit of noise.
You see how it's very poor during normal waking hours, and then great from about half past midnight to 9 am? Shows that the network and your hub are working perfectly when there isn't too much traffic. The most probable cause at this point in time is upstream over-utilisation (local network congestion), due to home working, home learning, video calls, gaming and live streaming uses. This affects the upstream because on a cable network, the upstream capacity is "hard coded" at a 1:10 ratio vs downstream in the current generation of technology that VM use, and that can't be changed in a timescale short of years. Which means that there's a very good chance that this will resolve when lockdown ends, assuming normal schooling, working and leisure behaviours return. Obviously your guess is as good as anyone else, but I'm thinking several months yet. Of little consolation now, but your BQM is a LOT better than many we're seeing in the forum, but that does give me a lot of confidence that the problem is indeed a temporary thing.
I happily blame VM for many things, but even I am forced to admit Covid wasn't VM's fault or anything they planned for, it's just unfortunate that lockdown affects DOCSIS cable networks far worse than most of Openreach or alternative FTTP technologies (they may have problems of their own, but not these particular problems). But I do believe VM have responded appallingly to both the consequent utilisation problems, mainly through silence or obfuscation, and their customer service provision has been wilfully inadequate for the past nine months (and was pretty poor beforehand). I don't believe VM will be working to fix this or most of the current crop of upstream over-utilisation problems. If it were quick, easy and cheap they'd do it, in fact they would have already done it. Your options:
1) Hope that lockdown ends soon, that all the Covid-related behaviours revert to how there were before, and hope that this does release pressure on the upstream, restoring a decent service. There's a very good chance this will be the case, but as I say, who knows how quickly.
2) Get in an almost certainly slower (but less laggy) Openreach ISP. Probably not a good option unless the poor latency is harming (or threatening to harm) your income or employment.
So there you have it, not your fault. And older. less capable hubs would have been trying to cope with fewer downstream channels, probably making things worse. I'd guess you got the hub swapped about the time that the latest lockdown started, and have copped the blame for the coincidence.
I did also mention noise. The yellow "fringe" of maximum latency on your BQM through the small hours is normal for a good DOCSIS connection, but them there spikes to 50 ms aren't. So I'd suggest you connect to the hub by clicking on this link http://192.168.0.1/ That should pull up the log in page for the hub. But don't log in, just click on the link "Check router status" That'll bring up a window with five tabs. Open the Downstream tab. Select all the text (Ctrl-A if using a keyboard), copy it (Ctrl-C), then paste it (Ctrl-V) into a reply here as text (not screen shots). Post that, do the same for the Upstream and Network log. You'll get an error message when you post the Network log, just click on "post" a second time. Then we can check for any obvious problems with power, noise or error counts. If there are any, they can be fixed, but they won't make much difference to the daytime over-utilisation issue.
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