The next step would be to verify whether the trip actually did post to FI and see what it looks like, if anything is missing.
From PR05, highlight the trip in question and then follow menu path Extras -> Payment history. There you should be able to see the accounting document that was posted.
You can take that document number and use FB03 transaction (Display Accounting Document) to display it in Accounting. Compare it to other documents posted from Travel and see if it looks any different. if any elements are missing.
Hopefully that will provide some clues.