Have had recurring issues with unstable cable modem signal levels for ever, been a customer for 19 years, started with Terayon modem and 64kbps service, it's always been an issue with with the local cabinet, new modems, NTL250, Hub 3.0 have been better at hanging on, but it's getting worse. In the summer a tech checked/replaced all connections, but said he could see the problem at the cabinet and had escalated to "Networks", but all he did was push my local downstream levels to +9dB so when it starts bouncing around rarely goes below -3dB. Was down again on Monday, and managed to get fault booked via mobile phone. Different tech doesn't believe any problem with the cabinet, wasted his time replacing my early white Hub 3.0 with a new Hub 3.0 and local cable/isolator again.
Today the connection just as bad as ever, the sun is shining and power levels bouncing from +9 to -1 when viewed, multiple partial/loss of sync in the log
Seen comment elsewhere about effect of Sunshine, can affect xDSL style connections due to noise injected into the electricity network via solar panel invertors apparently. Not really hot enough weather to cause local cabinets to overheat? My neighbours do have some solar panels...
It was rebooted and finally connected at 1:15 yesterday, the counters stayed zero and log quiet well into the evening. I was told by a previous tech that it's just a coax amp in the nearby cabinet. SNR ratios do not seem to change which suggests to me an amp somewhere is unstable, and if it's a dumb amp might explain why they can't interrogate remotely? Latest one insisted it is fibre to local cab ... but he didn't even open it.