DLM is lowering my upload speed

Little background - I switched to PN from Sky at the end of July have not had any issues with the line before this (and honestly I'm doubting that this is a line issue, but I'm just looking for some advice on whether this is worth pursuing with PN).

So as I said, we switched to PN, and 24 hours later DLM decided to drop my upload from 20Mb to 15Mb.
PN did a DLM reset, went back to 20, but 24 hours after the reset DLM dropped it to 15Mb again. My thinking at that point was that maybe there was a genuine issue and I'd leave it alone. Line has remained fully stable for 24 days before this last reset.

I've spent the last 24 hours hammering the upload (uploading a ~100GB file) and last night DLM kicked in again and has lowered my upload to 12Mb. The fact that this has occurred right after a heavy upload session is what's making me question it.

The Plusnet router (Plusnet Hub Two) seems to suffer from bufferbloat quite badly (BQM goes mental when uploading/downloading), but I didn't consider this to actually be a massive issue as the connection was still working fine, even when a big upload was in progress.

One thing that might be relevant is on the day of the switch, Sky decided to send an engineer out (Was triggered because I went through their self-check thing because I was trying to get a number for tech support because they had cut me off before PN took over the line, I didn't request an engineer (backed out when it said I needed one as I knew that the problem wasn't a line one) but they sent one anyway who fitted a little box where the phone line enters the house (looks like it's just a cable housing, I think he might have re-welded the line or something?)

Line stats suggest that the line is still quite capable of doing 20Mb and when they did the reset it did work fine before it downgraded itself again. BQM looks a bit messy, but as I said, this is usual for this router when connection is being hammered (and it has been hammered all of yesterday) download is fine.

Apologies for the long post just trying to capture all the relevant information.

So my question is - is this worth pursuing with PN? Is there maybe an issue with the router? Or should I just live with it, as they already did one DLM reset and it didn't help?

Line stats: https://i.imgur.com/ILn3jh2.png
BQM: https://i.imgur.com/WLgdZds.png

Product is FTTC 80Mb and download is completely unaffected

Edited by severedsolo (Sun 03-Sep-23 11:10:21)