the drop-down icon if used from a font-file, which has to be downloaded (e.g. /wordpress/wp-content/themes/astra/assets/fonts/astra.woff or .woff2 or ..). if for whatever reason the font-file is not downloaded when the page starts rendering you’ll (generally briefly) see a placeholder (the small square from your screenshot).
now as the Astra font-file is loaded with font-display: fallback;
in the Astra CSS, the time the browser waits for the font to be available is short, hence sometimes the placeholder will not be replaced any more.
and here we come to Autoptimize, which is not related to the problem but which might help; go to Settings -> Autoptimize -> Extra and add https://woodandlee.com/wordpress/wp-content/themes/astra/assets/fonts/astra.woff
in the “preload” field, this should -for browsers that support woff- ensure the font-file is available sooner.
hope this helps/ clarifies,
frank (ao dev)