Short Version
How can I get frequent disconnects of my BT FTTC service diagnosed? The drops are completely random as to time of day or night, there's no audible noise on the line & the drops are momentary. Although being a Huawei cab reconnection takes around four minutes. These drops are up to an average of daily over the last month & seem to be getting progressively worse. I had three in the space of nine minutes last night. I don't think it's environmental, either internally or externally, due to random timing & the fact it will happen of a dry, calm, sunny day.
Given the above, any regular line test by BT is going to report NFF due to the intermittent nature of the drops. Is there a specific test that ISPs can run themselves or ask Openreach to run that might shed some light on why this is happening?
Background
I'm around 500m from my local cab & have historically only achieved a max download of 35-40mb. My connection would typically stay up for around three weeks between drops. At the beginning of August I noticed speeds increasing to 50mb & that BT's ADLS checker was now reporting the potential for 60mb. So as I was on Fibre 2 at Fibre 1 price anyway, I asked for the profile to be uplifted from 55/10 to 80/20.
After a period of line training I started getting a consistent 70/12. The router (Fritzbox 7530) reports that G.INP on which I guess explains why the download is nearer max than the upload? But as above, I'm now getting near daily drops of the connection.
During the training process after the regrade, I seemed to get higher speeds in the test socket of the old NTE 5 with the MK3 faceplate removed. So I've replaced the master with a 5C with MK4 faceplate. That's given me fairly stable speeds but made no difference to the drops. There is no extension wiring.