Even after being "fixed", my connection is still u...

Question

Been with BT since late December, using infinity 2 with HH5. Live in a block of flats.
When we first got the package we were being disconnected every few hours, often several times per hour. Finally got some help from a mod on here who ran some tests and found a possible error on the copper line. BT sent out an engineer who fiddled with the cables in the ground outside, and things seemed more stable. Another engineer came out to reset the profile, and he also discovered line problems (something inside the flat's junction box or some such, in the main corridor cupboard for the block of flats). We didn't get any speed increase as hoped (in fact, we're now getting 3mb LESS upload), but the connection at least seemed more stable.
Fast forward to March, and now some of the old troubles have returned. We're not disconnected as much, but there are plenty of spells where we'll randomly get huge packet loss, which makes internet usage nearly impossible (webpages wont load or take ages to load, ping times in online gaming nose dive, NowTV app on the Xbox will keep dropping out, etc). Sometimes these spells last 5 minutes and then all is normal, while other times they'll keep returning in 5-10 minute batches until we give up and reset the HH5 (which often causes it to settle back to normal, though not always).
For what it's worth, I've not spotted any common denominator during these spells. No incoming calls, no random devices running which might interfere, no changes in browsing habits). I already disabled/fixed/changed the usual things people tell you to (the auto wireless thing in the HH settings, wireless channels, etc).
Here are some examples from PingPlotter which give you some idea of what's going on:
1. A 10 minute spell of packet loss. You can see the normal stable connection to the left and right of it.
 2. Another 5 minute spell of packet loss (with a couple of red bars in showing no connection at all), and then the big red block is after we reset the HH. Note the perfectly stable connection right after.
 3. One of the crazy 30 minute batches of packet loss. This one happened overnight (often we'll try to use the Internet channels via the YouView box in the morning and it'll say no connection, despite the connection being fine (at the time), and we'll have to cycle the HH yet again).
 4. A wider snapshot over the course of 2 hours. Internet connection will vary wildly between working as normal and then 5 seconds later being unable to load a page, then back to normal, and so on.
 5. Even wider snapshot over the course of 24 hours or so. Lord knows what was going on.
6. Snapshot taken just now. After a couple of spells of 5-10 minutes mass packet loss I spotted another one coming (15:24) and did a HH cycle (big red bar). Upon reconnection the graph shows things being pretty unstable, until finally the HH disconnected again (big red bar at 15:42) by itself. Currently it's still unstable as above. I expect another disconnection wil be forthcoming.
I'm loathe to manually reset the HH as I know that's not healthy, but if I don't do it we'll just get these spells of massive packet loss over and over again until it just disconnects itself (and it'll happen at inoppertune moments, such as during an online game, or while we're doing online banking, or while we're watching a footie match on BT Sport). I'd rather control when it disconnects myself and pick the right moment. A common war cry in our household has become "I'm resetting the hub, stop what you're doing!"
Now, I'm not some perfectionist that demands a 100% stable line 100% of the time, but frankly, while with *cough* Sky *cough*, we went for years with barely a disconnection in sight. I almost never had to manually reboot it. You'd think the supposedly superior Infinity would be at least comparable, but it's been nothing but trouble. This situation is especially annoying as Youview needs the connection for the TV channels, and we're either losing them entirely or they're breaking up at random intervals. 
At some point I may have to fork out for one of those Openreach modems to see if that helps, but it shouldn't be up to the customer to fix a problem, that shouldn't really exist in the first place, by paying out of their own pocket. 
Does *anyone* have any advice, here? We're locked into a million year control now so leaving isn't an option, and you'd think if there was an obvious, major problem with the line they'd have spotted it and fixed it last time. Users? Mods? Buddah? Anyone?

Answer 1

I've contacted the mods about the problem (again). Hopefully someone will check this thread.
For reference, here's a PingPlotter graph which shows me going from wireless (18:46) to wired (18:48) and back to wireless (18:56) during one of the evening's usual bouts of nonsense.
So yes, most of the chaos is with the wireless rather than the wired. Problem is, the full hub disconnections affect everything (wireless AND wired devices). Before someone says "well change your wireless channel!" or "investigate interference!" -- two points: 1) wireless devices are absolutely perfect for 90% of the day, and 2) there are random disconnections of the hub (orange light) interspersed with the wireless problems, and sometimes completely divorced from the wireless problems.