It sounds from the OP that the DCOE (Dedicated Centre Of Excellence?), which is who Openreach engineers contact to have any changes made (port swaps, DLM resets etc) , can manually set a specific DLM profile.
When the OP said earlier in the thread...
They offered to enable interleaving on the upstream part of the connection (one of them said he sometimes used to enable interleaving on ADSL connections to reduce packet loss), so I will see what difference this makes.
I was thinking to myself that isn't possible perhaps the engineer is indeed getting mixed up with ADSL, but then he posted a screenshot of interleaving enabled on the upstream.
I've certainly never seen a DLM reset result in both downstream and upstream interleaving. On an ECI cabinet it's always just downstream interleaving that's enabled.
If that's the case they can manually set the profile then it does seem a rather pointless exercise if the DLM continues to run and a few days later simply changes the current profile to remove the manually set change.
There was quite a few DLM related briefings for CP's during 2021 which might also explain it.
https://www.openreach.co.uk/cpportal/updates/briefings?t=category:briefings/super-fast-accessThey included a new
DLM Stability Policy Trial started in June, extended in October (trialing a new/different stability policy)
There was also a
DLM Reset Process Improvement Trial started in December.
It's possible this new stability policy trial starts with upstream interleaving and that's why the OP had it but also possible the DCOE manually set that profile.
I wonder if
BlackSheep is around and could enlighten us as to whether the DCOE has the ability to manually set a specific DLM profile (interleaving on/off, G.INP on/off, SNRM target) and if so whether they can make that change permanent and effectively disable the DLM from making further changes.
It's certainly something I've never seen before and wasn't aware was possible but if anyone could do such a thing it would be the DCOE.