Thanks James.
I am still convinced that this is a WordPress bug. And even more so now after reading through the posts on this site about it like this one:
https://wordpress.org/support/topic/failed-to-import-invalid-post-type-possible-workaround?replies=3
Hopefully the next release of WordPress will address it and the Import Feature will again work properly in future versions.
Thanks again and have a wonderful evening.
Jenny