Indesign locks up when exporting to pdf

You can export as single pages. The page after the last Page causes the problem.

You could try 

Exporting the first 50% of the pages if that works try the other 50% of pages - whichever side it fails on is where the issue is. You can keep dividing and conquering the pages to track down the pages with issues.

Other methods to try:

Could you try using File>Export and choose IDML - open that up in InDesign - resave as an indesign document using a new file name.

Does the issue persist?

You could try:

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Try resetting your preferences:
The easiest way to reset everything is to delete the InDesign preferences: as soon as InDesign starts to boot hold down Shift, Alt, Ctrl (and Apple/Cmd if working on a Macintosh). A dialog will appear asking to delete the InDesign Preferences, select 'Yes' on this dialog.
Further info and instructions here if needed:
https://helpx.adobe.com/in/indesign/kb/indesign-preferences-support-file-locations.html

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You can always try the creative cloud cleaner tool https://helpx.adobe.com/creative-cloud/kb/cc-cleaner-tool-installation-problems.html

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Rollback to previous version does it work again?

https://helpx.adobe.com/download-install/using/install-previous-version.html