I've been using the default "fancy" pagestyle for as long as I remember with the section as the right header and the subsection as the left header. I just dug up a document from April this year (will be an important detail later) and it looks like this (which is what I want):
This is where the current section is "The Set of Real Numbers" and the subsection is "Irrational Numbers".
I now recompile the same document without changing anything in the source and this shows up instead:
(Note there is a contents page which is where it must be getting that mark from, but previously it would never cause this to happen.)
That's why I had to get a document back from April - I've been playing with some other documents and without fail, compiling the exact same code causes the section to flip to the left and "CONTENTS" to show on the right on every page. I can't find a way to revert it to what it was before.
Really stumped here - any help would be much appreciated.