Exporting gives error and fails.

Have you examined page 42? Are you able to export that page alone? Can you export pages 1-41? 43-?

In terms of the serious solution question yes, if you start a new document with the same page size, margins, etc., you can use the Move Tool from the Pages Panel and select the new document as the target. This works for some things, but not always.

Another thing is - maybe just restarting InDesign - or rebooting your computer can free up resources without any major cleanup of files etc. necessary. It might work after trying this, it might not.

Your other option is to try File>Export and IDML (first thing I'd try) see if opening that and resave as a new name solves the issue (try export after saving as a new file).

If the issue continues

Duplicate your document (always test on a copy)

Divide and Conquer

• Try exporting half the pages, then export the other half.
• If one half fails but the other succeeds, keep splitting the failing half in two and export each section.
• If both halves fail, start by exporting page ranges say 1-20 at the start and 230-250 at the end for example, then keep dividing until you isolate the problem pages.
• Once you’ve found the troublesome page(s), try exporting them on their own.
• If they don’t export, remove elements one by one  text frames, images, shapes, or anything unusual  and test the export after each removal.

Whatever element allows the export to succeed is your culprit.

This sounds long, but the process goes surprisingly fast.