as you were able to get dslchecker results using phone number that suggests you are not yet on digital voice so can you try dialling 17070 option 2 on home phone and it should be dead silent
your stats show attainable speed of 67mb so there is a line problem switching off every night as already pointed out is not helping your connection
Turning a router off a night and bad on in the morning won’t be interpreted as instability and cause DLM it intervene …repeated power cycles would , or as would issues on the copper pair .
As can be seen , your max attainable is 67Mb , your sync rate 48/49Mb so room for improvement, the target noise margin is 6dB or on some cabinets 3dB , your noise margin at 6.8dB.
Personally I would for a while relent on turning off the power at night ,and check if the noise margin improves, it’s possible that your line is banded because of previous instability, and occasionally it can take a while to be removed even when the instability has gone .
Finally , have you checked your line for noise ( dial 17070 quiet line option ) any noise , report it , you could ask for a OR visit , and ask the tech that visits that they get your profile reset , ( if the banding is sticky ) , and if reporting to BT , I would put the SH2 back on as your router isn’t supported , if there is a external problem getting the profile reset is pointless as the instability with simply cause DLM to intervene again , so if there are issues they need addressing
Not much point in the OP trying the quiet line test as he explained in the first post "I'm hearing disabled so can't make phone calls". Obviously, he might be able to get a relative/friend/neighbour to check for him but that an be difficult sometimes.
@imjolly& @iniltous - I'm hearing disabled but my wife helped with the quiet line test (17070 then press 2). She said there was a low level steady hum (we have a cordless phone) but no pops or crackles.
I'll obviously need to power cycle when swapping over from my ASUS router to the BT HH6 but I'll keep the hub on 24/7 thereafter.
Incidentally, I've never had a BT engineer over my door in the 40 years I've been at this address, so I don't have a master socket but do have filters on the line to my hub and the line to my phone. The BT hub which was supplied in 2017 is labelled HomeHub 6, which I believe is the same as SmartHub but is not the latest SH2. I substituted the ASUS router to give me better control over my wifi and connected devices for visiting relatives.
a dull hum is normal when using cordless phone so it suggests you have an external line problem and probably need to get engineer visit to sort it out you are as previously suggested in a banded profile due to the drops in connection and this will not correct itself unless you can get a stable connection for 7/10 days which at present seems unlikely hence openreach visit
when you get visit make sure openreach person resets the DLM and gets your speed back before he leaves
Many thanks to all for advice and suggestions.
Before I request an engineer, I think it wise to refit and use my BT HH6 for a few days to see if that fixes the line drops. If it does, that would suggest my ASUS router has developed a fault.
If the line dropping issue goes away with the BT HH6, I'd guess the DLM will still need to be reset to get my speed back but would an engineer visit still be needed for that ?
if you put the HH6 in and line then is stable the DLM should after 7/10 stable release the banding and speed should increase toward attainable 67mb
UPDATE
Reverted to my BT HH6 yesterday afternoon.
Initially it reported;
VDSL link Up: Down Rate=55953Kbps, Up Rate=15455Kbps, SNR Margin Down=6.10dB, SNR Margin Up=7.90dB
I ran the 'Broadband performance test' which reported a problem so I then ran the troubleshooting and this eventually opened a web page saying there was a fault on my broadband line 'outside the home' and an engineer visit has been booked for Wed 11th October.
I checked the hub stats after the tests and got the following;
VDSL link Up: Down Rate=35808Kbps, Up Rate=14999Kbps, SNR Margin Down=0.00dB, SNR Margin Up=6.00dB
I didn't like the drop in speed or the zero download SNR margin, so I clicked 'Restart the Smart Hub' and after the restart the stats were as follows;
VDSL link Up: Down Rate=27024Kbps, Up Rate=15159Kbps, SNR Margin Down=5.90dB, SNR Margin Up=6.00dB
Going from bad to worse.
At the moment, approx 22 hours later, the technical log is now showing;
Data rate: 15.00 kbps / 27.65 kbps
Maximum data rate: 15159 / 27024
Noise margin: 6.7 / 16
I have included below screen shots from yesterday afternoon showing the Status, Technical Log and Event Log (WAN) after the test and restart. I will leave things as they now are and keep the hub switched on and post a further update after the engineer visit or sooner if there are any dramatic changes.
Nothing is going to improve until the line fault is fixed.