I have the same symptoms.
Occurs when window size is less than 1153px.
At that time #site-header-main is position: relative
, And a gap of the header size setting occurs with #header-image-main-inside.
It was understood.
But this setting item is still left and might invite confusion.
In addition, it is hard that a text (mainly a title and contents) is not displayed well when I do not use the custom CSS.
Because I understand CSS, I make custom CSS.