Mac Mail: MBOX import/rebuild loses attachments

I have an MBOX that is corrupt.

If I try to import it into any exporting tool (like MacUncle MBOX to PDF tool) or Thunderbird (using ImportExportTool) the folders and mail come across EXCEPT any pieces of mail that have an attachment. They are just ignored and the tools only "see" the emails with no attachment.

If I try to rebuild the mailbox from within Mac Mail, it just deletes any mail with attachments.

Before rebuilding, if I choose any mail with attachments, I can export it to PDF and I can download the attachments, so they are "there".

If I import the MBOX master db into Mac Mail, it strips all the folders (mailboxes) and imports all the mail into one "imported" folder. Those still have attachments until I rebuild this and poof all the mail items with attachments disappear.

Any ideas? Help? Thank you!