I hope you understand now kitz why I said it would make sense that the 3db profile would be hauwei only to start with as it seems we starting to see unexpected behaviour on ECI g.inp lines.
Not really for the following reasons.
Same thing appears to be happening on at least some Huawei cabs.
FEC count alone shouldn't negatively affect DLM.
If it's going to work the same way as 21cn DLM, then 6db will still be standard and 3db will only be applied to lines with ILQ green.
From what I can see on my own line, the FEC has got to be occurring at the DTU, perhaps it gets busy once per day doing something else at that particular time.
3db doesn't need G.INP, but G.INP will make those lines on 3db more stable.
3db was already trialled last year over various cabs. This trial now is large scale involving ~100k lines, but it's still a trial so can be stopped any time they like. I strongly suspect that they deliberately delayed this larger trial until after the eci cabs had been upgraded. If they would have wanted it to be Huawei only, then why wait until now... they could have easily continued where they left off last year.