Sticky table header on Gin theme does not scroll horizontally

When using the Gin admin theme: If you select a lot of roles to be visible, to the point where the permissions table requires horizontal scrolling, the table header will not also scroll left/right in sync with the row of permissions checkboxes. This makes it hard to know which checkbox belongs to which role, and can lead to accidentally enabling permissions on the wrong role.

To reproduce, use the Gin admin theme. Create a large number of roles (e.g., greater than 10.) Go to the permissions page, select any provider, then select all the roles. Narrow the width of your browser until you see a horizontal scrollbar for the permissions table. Scroll to the right. The table header with the role labels does not move in sync with the row(s) containing the checkboxes.

If you recreate these conditions in the Gin admin theme without the Better Permissions module, the table header does scroll in sync with the permissions rows. So this appears to be a problem in the Better Permissions module, possibly related to Ajax reloading.