The “Disable Featured Image replacing header image” box is ticked and I disactivated all plugins as well, but no change. When I change the “Header image size” to something else than 198px, I have an extra image file of that new size after uploading. So the extra image IS created to be a header image.
I can’t be a 100% sure, but I would almost say this started happening after I updated to the theme’s 1.8 version.
