When trying to print in the spreadsheet (from an excel imported sheet) , blank areas appear. These only appear when trying to print. You can see the blank box area on the preview pane when printing, and the blank areas appear on the actual print. You can not see the blank box in normal sheet edit mode.
You do NOT see the blank areas when you use the preview button from within the sheet, but if you print the sheet you will again get the blank area.
If you export to pdf you not get the blank box.
If you then close libre office and open the same sheet in excel you will see that in normal view a blank box, sometimes multiple blank boxes the same size on top of one another have been inserted which can be moved, deleted, resized etc.