On a similar subject, Transport for the North have produced a new document, focussing on central Manchester but focussing on the impact across the north.
https://transportforthenorth.com/wp-content/uploads/Item-5-Central-Manchester-Report.pdf
The report recognises that punctuality in the north of England, Merseyrail apart, is the worst in the country.
It also recognises that the line to Manchester Airport and the line between Manchester Picadilly - Stockport appear to be able to be classified as 'congested infrastructure'.and that delays from congested areas around Manchester ripple out across the north.
We frequently see TPE trains to Cleethorpes and often, as a direct consequence, Barton Line trains, delayed as a result of this congestion and indirectly by the officially conjested infrastructure in the Castlefield Corridor, on which trains from Liverpool are frequently delayed, causing knock on delays in the Hope Valley.
There are long term proposals to improve capacity in all three areas, however in the short term it may be necessary to temporarily reduce some services around Manchester in order to make the timetable more resillient and thus improve punctuality.