Wild swings in BT Infinity 2 sync rate.

Question

Got connected at the start of July. BTHH5 listed maximum data rate at 21000 something up, capped at 19999 and between 73000 something and 74000 something down. After the modem decided to start chucking off the wireless devices, a factory reset was required, which reduced the down by about a 1000 or so. Then a couple of weeks later, the maximum data rate went up to 97000 something down, capped at 79999, and 33000 something up, capped at 19999. This was clearly good news, as speed tests now came out at 75 meg down, and the same 19 meg up on the iPad Air, while as the previous down throughput was 67-68 meg at best. Now I know these are good figures anyway, but considering we live so close to the street cabinet, I'd thought we might get the max speeds anyway. Ex hurricane Bertha comes through and the max line speeds dropped back to their previous values, although curiously as the modem didn't re-sync, we maintained the higher sync rates. That was until today, when the HH5 played up again, this time bringing the 5Ghz band only used by the iPad to a grinding near halt, while the 2.4Ghz band continued as normal. Another hard factory reset seems to have cleared that, but the modem has now synced at the lower speeds again. Is there anyway of regaining the faster sync speeds, or do I just have to wait another few weeks and see the sync speeds increase again? These are the current stats,
1. Product Name: HomeHub5
2. Serial number: +076284+1402007930
3. Firmware version: v0.07.01.0235-BT (Type B) Last updated [Unknown]
4. Board version: 01
5. VDSL uptime: 0 days, 00:21:39
6. Data Rate: 19999 / 72757
7. Maximum Data Rate: 21196 / 72761
8. Noise Margin: 6.8 / 6.1
9. Line Attenuation: 0.0 / 10.3
10. Signal Attenuation: 0.0 / 0.0
The noise margin figures increased significantly when the faster sync rate was achieved, I thought it should be the other way round? The line attenuation has always been either 10.3 or 10.4 down.

Answer 1

We have in the past had occasional noise on the line, usually after it's rained hard. This has led to a complete loss of phone and broadband service. Initially the line has been completely dead, followed by a return of some dial tone, drowned out by a hissing, scratching noise, etc, with the phone ringing randomly. Obviously have reported this line fault each and every time to BT. However by the time they come round, 3 working days later, the fault has gone and they can find nothing wrong. Been repeatedly told they can't do anything unless the fault is present when they come round. I tell them, well come quicker then, which elicits a blank response, and the cycle continues. I've been told it's probably a battery fault. This hasn't happened for some time (touch wood). The last time, the line just went completely dead. They switched the line at the street cabinet, which led to the line attenuation increasing significantly on the old router stats, and a drop in ADSL2+ sync speed. Was suggested that they may have piggy backed the line to another adjacent street cabinet. There often seems to be someone there doing something. Many people in our street and beyond have had the same problems, with loss of service in some cases in the weeks!
P.S. The previous HH5 hard factory reset required all the wireless devices to be reconnected manually. This hasn't happened this time, all the devices just picked up the connection again. Is this normal? Could it in some way suggest that the hard reset wasn't a hard reset, even though I stuck the pin in the back of the modem?
P.P.S. I can't do the quiet line test at the moment.