Empty content frame in Header Highlight Content

I have a quite strange problem on my site www.spesistockholm.se. I am using Lucida Pro v1.6 with a child theme, and Header Highlight Content with nine pages/frames. Some browsers, for some of my visitors, puts an empty frame between 3 and 4, pushing frames 4-9 one step making frame 9 the only frame on a new row. https://www.dropbox.com/s/445eev2aaj0s5zj/mosaik.JPG?dl=0 I have tried to recreate the problem with Firefox, Chrome and new Edge, both logged in and not logged in, and for me it always works. But not for everybody apparently. Does anyone have an idea what to do?