This is a very minor visual bug, whereas if you want to print a biblio details page in staff interface (/cgi-bin/koha/catalogue/detail.pl), along with its items, by using either Ctrl+P or the designated Print button at the top, the checkboxes and "Modify" buttons on the right are visible in the items table. Ideally the CSS should be modified in the way that the whole checkbox and buttons columns are hidden in the @media print view, because they don't belong on a printed page in any way and look just out of place in an otherwise relatively neat print view.