Hi Yaron,
This is not an error, HeaderTabs has been working for me for many years, so thank you for that! This is more a design issue as more and more people start reading websites on small devices like smart phones. As far as I know it is currently not possible to have HeaderTab configured such that on small devices a hamburger or tri-colon button would appear to minimize the tabs to a dropdown menu such that each tab still can be selected, also on small devices to get to part of the text. Has this come up earlier (couldn't find it here) and is this something you like to consider including in upcoming versions?