InDesign freezing on export after loading recent update

It's my experience when you update InDesign that you need to rebuild the book file.

Try creating a new book file and importing your documents again.

Other options

Try exporting just some of the documents

if it crashes on some but not others then you know it's the document and not the book file itself.

You could try documents 1-5 in the book then documents 6-10 etc. 

If it's a certain document

If a document is not behaving well then try 

File>Export 

Choose IDML

Open the IDML in InDesign
Save the file as a new InDesign file with a new name
See if the issue persists.

Other options

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Try resetting your preferences:

Windows: Start InDesign, and then press Shift+Ctrl+Alt. Click Yes when asked if you want to delete preference files.
macOS: While pressing Shift+Option+Command+Control, start InDesign. Click Yes when asked if you want to delete preference files.
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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Reinstalling rarely fixes everything - you can do a complete reinstall using the
Creative Cloud Cleaner Tool https://helpx.adobe.com/creative-cloud/kb/cc-cleaner-tool-installation-problems.html

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Rollback to a previous InDeisgn version

https://helpx.adobe.com/download-install/using/install-previous-version.html#:~:text=Open%20the%20Creative%20Cloud%20desktop,down%20list%2C%20select%20Other%20Versions.