I’m struggling with this same issue and neither solution above works for me. But the problem doesn’t seem to be caused by the featured image. In my case, it’s happening because my site title is too long. When my Title is “Life Transitions Workshops” the mobile menu displays incorrectly using either solution above. If I simply change the Title to something shorter, like “LTN” the menu floats elegantly in the top right corner in portrait and landscape modes. But the shorter title isn’t a good solution either.
Can the code be tweaked in some way to tell the menu to ignore the title text?
(I didn’t start a new thread because this seems to be the same issue as originally posted. His site title is also pretty long and I suspect if it were shortened the menu would appear correctly. If I’m wrong about that I’ll start a new thread.)