I’m having a bug when hooking header elements with a navigation block. The navigation blog gets buggy, only on the front-page (Id of the page) (see first link).
Not sure if it’s a problem on your side, or with the navigation block.
that is odd, ill have a play to see if i can replicate the issue.
But can i suggest that you use the Themes Site Header and Navigation instead of a Block Element the core Navigation block, as the core block is not particularly great….