That is an interesting question and I don't have experience of document corruptions at the section level but I will add some suggestions.
1. If you believe a corruption exists in a particular section break, you should be able to simply delete that section break. The attributes of the following section will flow backwards into the content in front of the section break you removed and theoretically remove the corruption. It would be interesting to note if the corruption you 'deleted' by this action is removed or transferred to the subsequent section break.
2. Rather than copying content to another file section by section, I would use a replace all function to replace all section breaks (^b) with a paragraph mark (^p) and then do a single copy/paste to a new document. This is something I often do to minimise clipboard complexity and adapt the page setups when I paste into other documents - I just don't do it for the purposes of removing corruptions.

In my experience over the past 10-15 years (touch wood), I've not seen a corruption that was only solveable by copying all to a new document. I have a hunch that the 'copy almost all to a new document' actually doesn't achieve anything with the docx format files (although it still might with doc format files) but I do agree that 25 years ago it was a useful practice that still gets passed on through folklore. I'm happy to be proven wrong but I just haven't seen enough corrupted files of late to be able to narrow corruptions down to the section break or final return.

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Andrew Lockton
Chrysalis Design, Melbourne Australia