I just did a clean import of DNN 9.4.3 and exported the site. The export completed quickly (little content added and just the default pages and modules)
I was able to import the portal I exported.
Using the default website, I exported. Then deleted the content on the home page and imported the previous export. All was fine, and both the import and export completed normally.
Check the event viewer and also the logs in /portals/default/logs to see if there is anything useful there.