Export failure from WordPress install

Probably because the tool encountered an unexpected data structure. You’d be better off asking the developers of the export tool. But without being able to examine your site’s raw data, finding the problem could be very difficult. Personally, I’ve frequently had issues with various export tools. I now generally manage export/import manually through the phpMyAdmin app. It’s a little intimidating at first, but it gets much easier after you’ve done it a couple times. I’ve never had any issues by going this route.

As long as you still have access to the source data, there’s little to lose in trying the manual method other than time spent 🙂