John, you might wish to temporarily uninstall or disable any 3rd party anti-virus or malware protection (I use win 10 and rely on defender). A number of packages severely degrade performance and can interrupt WX5 writing files as they are scanned.

Please make REGULAR iwzip files (step 5 export project and add the date to the file name on creation) otherwise you will lose the project eventually.

You may wish to import one of these iwzip files (this will not overwrite your existing project) and see if the new program is more stable. If the pages have large content (big image files in particular) you should save before preview, and if the changes you are making affect more than one page (eg header/footer/structure/sticky bar) do a CTRL+preview.

There is an option in step 5 export project to optimise images, if you suspect large image sizes could be the cause you might want to try this.