To reproduce the bug: - Use Mozilla Firefox 48.0 or 53.0 (these were tested) - Add title to cart in OPAC - Open cart - Click the link "Print" - A printing dialogue appears - The popup window with cart seems to refresh in the background - A second printing dialogue appears (placed exactly over the first one) - Sometimes these dialogues do even crash This was tested on a Koha 16.11.0, Koha 16.11.4 and on the current Koha master. This was also using Opera 12.16 and Chromium 58.0 - these don't show this behaviour.
Tested on top of Bug 18545 with Firefox 53.0 (Win) and Firefox ESR 45.3 (Debian). Prining behaves now as expected. *** This bug has been marked as a duplicate of bug 18545 ***