When I print out a page in Calc, the upper left quarter of the page is covered by two overlapping blank boxes - kind of like text boxes. Blank white boxes bordered with single lines. These do not show up in Print Preview.
Without a sample file not easy to know. Search with Menu/Viiew/Navigator [F5] if exist those boxes.
I never was able to find the cause. I tried copying all the cells onto another page, but it just carried the issue with it. So I ended up simply inserting blank lines to push my desired spreadsheet lines down past the “boxes”, then copied my desired lines onto a new sheet, and deleted the original sheet. No problems since. It’s not really an answer but I consider this issue resolved for my purposes, and will close it.
Today I experienced the same phenomenon: a page which I could print previously without issues is now “covered” with a white box (5 columns x 55 rows).
The “box” is not visible in Libreoffice page preview, but only in the printer dialogue menu and on paper.
The box disappears, when I un-check “drawing objects” (Zeichnungsobjekte) in Libreoffice page settings.