Two answers.
Firstly, the second, lunchtime, path has been in regular use for at least two weeks now. I don't know if it is additional business at the ashburys depot, but I seem to recall reading somewhere that work coming up soon, at or near this depot, may block access for at least several days. In which case, they may be building up a stockpile.
Secondly, over and above the gradient issue leaving Buxton, and the problem that trains using this line are delivered to Stockport often facing the wrong way for onward movement, there is a very weak bridge in Whaley Bridge which NR have been trying to replace for several years. The local authorities have been blocking all attempts to do this on the grounds that they do not want additional freight through their village "we have our road bypass so the rest of you can go hang".
No doubt, one day this bridge will fail, and if it doesn't deposit a train in the road below, it will at least stop all passenger trains for several months while they rebuild it. Thanks, Whaley Bridge Parish Council, High Peak Borough Council and Derbyshire County Council.