Ummm this brings back memories...
We used to get cut off all the time....finally an engineer came oot and spotted the transformer - as in mains plug into the ambit 100 modem
... Haha he chortled and disapeard to his van returning NOT with a new modem as I'd hoped....but with a new plug...the third in a year....
Look he exclaimed proudly, this plug has a sticker on it that says NEW...there's a known fault you know with some of these plugs....
And off he went....we don't get cut off anymore, just the nightly hassle of high ping kicks and super low download rates...can'thave everything I suppose!
Hope this helps!