When browser window width is resized JavaScript is changing breadcrumbs layout to try to fit it on one line. It works well when window width is being increased or when there aren't any other items on same row of navigation.

Problem is, when browser width is being reduced, script assumes that breadcrumbs width should be the same or reduced. It doesn't consider possibility that breadcrumbs block could be wider. This issue happens when there are other items in same row of navigation that dynamically change layout (for example, changing big button to small icon for mobile devices). See https://www.phpbb.com/community/viewtopic.php?p=14018981#p14018981