I’m not sure how this makes any sense but found that this header height issue is caused when any of the browsers are in a “zoom” mode. My IE was set to 110% and when I set it back to normal all seems good. Setting zoom lower than 100% seems to work fine as well.
I don’t know if there is a fix for this, but at least for now I can stop pulling my hair out staring at four lines of code wondering what was different. 