I'm still confused and extremely unhappy about these issues, but (being careful not to breath to heavily) 3.8.8.2_BT still seems to be holding up OK on my 5GHz. I have no idea why (and have probably just jinxed it!).

I did have a bit of a wobble earlier today when I decided to see if 3.8.8.2_BT also improved another issue that I was experiencing... I purchased my 2862 to terminate my VDSL line and provide both NATted internet access and routed 'raw' access to the remainder of the /29 that I have. I previously used a zyxel router that was supposed to be able to do the above, but in the end could not properly handle the non-natted access simultaneously the the NATted access. When I set the 2862 up I found the VDSL interface to be extremely unstable. It was disconnecting a number of times daily, reporting a lower attainable max rate, a noise margin that was lower than the Zyxel (even when reporting the worse sync rate). It was just about clinging onto syncing at 80Mb (subject to maybe half a dozen reconnects a day). To put that in context, the Zyxel connects reliably at 80Mb, never causes a disconnect, and attainable connection rate is generally about 93Mb+/-3Mb. For the two years I've had that connection, DLM never had a reason to intervene, and my connection remained unbanded (not sync or rate limited by the DSLAM).

In a week or so of faffing with the V2862, It managed to cause DLM to intervene banding my connection at 76Mb. Than just at the end of that as I was engineering around that instability, further intervened me down to 70Mb. I connected the V2862 via ethernet to the Zyxel which is back to its 80Mb connection (after waiting for the 8 days doe the first tier of Banding to relax. The Zyxel has rock solid for thirteen days with no line drops.

Today I briefly retried the VDSL interface on the 2862 (just in case 3.8.8.2_BT improved that- unlikely as modem code version seems unchanged). the 2862 again did not seem to match the connection stats of the Zyxel, and I quickly put the Zyxel back in circuit. HOWEVER - whilst I was doing this testing, the 5GHz wifi on my iPad was slow to reconnect/flaky. It's back (apparently) stable now... Arrrrrrgggghhhh!

@piste basher: Do you know why your VDSL was being actively managed by DLM?. Some ISPs do now have the ability or order resets, but obviously the underlying cause of the intervention needs to be identified to prevent the de-rating reoccurring...

It's hard to know the root cause of the re-banding I experienced. I had been on a package with Zen for some years, for most of that time I was using the internal modem in a 2860 which was stable enough in itself but the need to re-boot the router almost every time I made changes to the config was frustrating. In any event, over a few years my download speed dropped from an initial 38Mbs to around 22Mbs (and I was paying for an "up to 80" service).

In the end I was fed up with paying for a service I didn't receive and threatened to leave Zen for a cheaper option. They persuaded me to sign up to a different package, up to 40 this time, which I did. That must have re-set the DLM profile as my speed immediately went back up to 38Mbs.

I was still using the 2860 but, wanting to go to 5GHz ac, I changed to a 2862ac, still using the internal modem. That was nowhere near as apparently unstable as yours but it would drop the connection every few days. I was also using a wifi router as a failover connection on WAN2. Thinking to see if I could get a more stable connection I bought a 130. That does indeed give me a stable connection but using that on WAN2 meant I no longer had my failover so I moved to a 2925ac (you can see that I have donated much to the Draytek coffers over the years).

Shortly after I started having problems on the LAN side - all lights on the 2925ac were "normal" but no wired or wireless device could connect to it, only solved by a re-boot. I still haven't discovered what was wrong but suspect it may have been a DNS problem. In any event I switched back to the 2862ac set up.

During all of this my download speed had been dropping in stages until around Christmas time it was 24.9Mbs. The last drop was in November and appeared to coincide with the fitting of a G.Fast pod to the side of my cabinet. I raised the matter with Zen who suggested the problem may lie with my equipment ( ) and that I should "monitor" the situation for a while and see if the DLM system put me back up.

So using the 130 and 2862ac I "monitored" the situation for 5 months, leaving everything alone. Still on 24.9Mbs. Another call to Zen, a different support person this time and an immediate willingness to re-set my profile. This was done, initially my speed went up to 29Mbs (with interleaving) then to 35Mbs (interleaving removed) and now on 37Mbs.

I have reverted to using the 130+2925ac with failover to the wifi. By removing all references to Google's DNS and letting the router pick up Zen's DNS I seem (touch wood) to have resolved the LAN problem as far as the router is concerned. However, if I let iPads connect to 5GHz on the AP902 the connections become very flaky - problems with slow connection or no connection at all, the "wrong password" issue etc. 2.4GHz is fine. They don't have any problems connecting to 5GHz on the 2925ac or, as above, on the 2862ac.

Re the VDSL issue. Zen are offering a free Fritzbox to new clients. Maybe see if you can do some arm twisting and wangle a free router from them, set that a modem or bridge the fritz to WAN2 (and compare stability/ connection stats etc to the Draytek modem). At least then you can get a feeling as to where the issue is rooted.

Zen will be as constrained as any other isp that uses openreach infrastructure as to what they can tweak, but at least the people are better there (I’m with them too).

How far are you from your cab?

About 250 metres in a straight line, who knows how long by wire :?:

I'm very reluctant to change anything now I've finally got my speed back, but I'll bear it in mind, thanks.