Is there some limits on how big the Title Header can be?
Those body parts should be visible in preview.
But preview previews all the records in your current found set starting with the first record in that set. That may not be the record you are looking at when in browse mode so you may have to "page" through the previewed document to find the one representing your current record. Or you could limit your found set to just the current record before entering preview mode.
(And there might be some other issue at play here so please report back with more info about your problem if I have guessed wrong as to why your preview isn't previewing the way you expected it to.)