Bookmarks get lost when creating new bookmarks

Hi, I've been having an issue with Adobe Acrobat for some time so I thought I'd post this in the hopes of either directing me to where a resolution can be found or informing the community of the issue.

I'm currently running this version of Adobe Acrobat Pro but the issue has been on-going in many versions over the years as far as I can tell:

I create Word docs in many languages and convert them from Word to PDF. When I'm creating a Japanese version of a PDF from Word 365 using the ribbon option, I get this issue in the headers (Issue #1):

I then attempt the same thing but from the Save As option. This appears to work fine but I now need to update the bookmarks to include the Table of Contents page:

I highlight the TOC's heading and click the "Add a new bookmark" button:

At this point all's well except for the placement of the new bookmark item in the listing.

The final task is to move it to the top of the Bookmarks listing, but if I do it now and save, close and reopen the PDF document I'll find that all the bookmarks have disappeared.

Instead, I save and close the PDF with the new TOC bookmark where it is and then reopen it ... but what have we here:

The new bookmark for the TOC is missing ... or is it?

If I click to expand the bookmarks, the TOC entry is now at the bottom of the listing:

At this point, feeling a bit queasy, I click and drag the TOC bookmark from its current position to the very top of the listing where I want it, save, close and then reopen the document and voila:

If anyone has any thoughts on how to resolve this or - perhaps - there's a setting I'm not familiar with to correct this please let me know - thanks!

The bookmarks issue isn't exclusive to the Japanese version of this document. This is an issue in any of the many languages I work with.