Header highlight content and SSL

I have a problem now and then with the header highlight content section. Up until now I haven't used SSL, and sometimes the images in the highlight content section would break because the address to the image for some reason had changed to https. Today I switched to SSL and the problem is reversed - the images are broken because the address http instead of https. When looking in the media library the address is indeed http, but mixed content is active so it should work anyway. Why do the highlight content section behace like this? The featured images in posts works on the start page despite the fact they too are on http, it is just highlight content section that behaves strange. The site is located at spesungdom.se.