Ive not examined Alecs line in minute detail nor read all the posts in this thread as I missed quite a lot during the period when I wasn't around so apologies if Ive missed something important.
However, from what Ive seen, there does appear to be something strange. Remember that the DLM had to intervene at one point because irrc the line was dropping sync a few times a day. Applying G.INP appeared to mostly correct things and g.inp had the effect of masking what was going on. If this is the case then the line possibly had some noise which g.inp sorted. Once g.inp was applied I couldn't see anything obviously wrong with the line.
It is rather strange though why DLM hasn't today done a total refresh and reset everything back to zero. I am hoping that DLM will soon realise that a g.inp modem is in place and will apply the correct profile