Hi MillardSewing ,
Thank you very much for your post.
I am not sure we can help here. Users we have are using the Export PRO with no issues and if they have any we try to help.
Yes, large sites with a lot of data may have issues and we can not guarantee you will not have them.
Your issue have a lot of work arounds as you can update data in bulk by category or any other filter so you reduce the volume and the import goes through.
Hope this helps.
Pavel