Hey Stephen,
I see what you’re saying now. Unfortunately there isn’t a whole lot of support we can provide for theme related conflicts but hopefully I can help to get you pointed in the right direction.
To start, I took a look at the javascript file that controls the header functionality you describe. One thing of note is that it relies on the “#main-content” div within the the template files for triggering that resize. However, by default, the events calendar template doesn’t contain that div.
So, to remedy this, you’ll need to follow our Themer’s Guide to copy the “default-template.php” file from the “views” folder within the core plugin and add the “#main-content” wrapping div around the contents there.
That should help to get the header resizing working on the events calendar pages.
Thanks!