Some headers are not sticky on My Portfolio

Some headers are not frozen when scrolling down the page on My Portfolio.  I need to scroll up and down to understand the nature of the numbers.  To summarise, the below does not work on My Portfolio: 

iPhone app (latest version): all headers not sticky

iPhone Safari / Chrome: all headers not sticky

iPad app (latest version): Headers in Dividends, Growth and Performance not sticky

Windows laptop Chrome: Dividends and Performance not sticky