In this doc file (attachment 122056 [details]), a large, mostly transparent image covers the entire page.  Because it is transparent, the text behind can be seen.

During export, the image is assigned a white fill (instead of none), and so on import the image's background fill now covers the text behind.

The same thing is happening with the frames of the two table in this document.

This happens as far back as I can test with bibisect 43all (LO 3.5).

I expect that a solid fill was added to every frame on export based on this old 2002 commit. https://cgit.freedesktop.org/libreoffice/core/commit/?id=ed8b5f2debac216243930aba0873e0d75de8d0dd

Caolán McNamara  on 2002-09-19 12:54:59 +0000
commit ed8b5f2debac216243930aba0873e0d75de8d0dd
#99657# handle no fill correctly for export


1.) Open LO Certificate Master.doc. Select the image (easy to do since it covers almost the entire page) and look at area properties. Notice Area fill is NONE.
2.) Save and reopen the document. Notice that a lot of text is "missing". Notice that the image's area fill is now color white. The same is true for the table frames.
3.) Delete the image and you will see that it was just hiding the text.