Legacy or previous styling loading?

Hello,

Issue 1: Flash of old menu styles (FOUC)

This is a Perfmatters delayed styles problem. Look at the bottom of the page source:

!function(){const e=["keydown","mousemove","wheel","touchmove","touchstart","touchend"];
function t(){document.querySelectorAll("link[data-pmdelayedstyle]").forEach(...

Perfmatters is deferring most stylesheets — including generatepress-dynamic-css (which contains your Customizer changes) — until user interaction. On first paint, the browser renders with whatever is in the critical/used CSS cache (front.used.css), which still contains the old all-caps, lighter-colored nav styles. A few seconds later the deferred styles load and the new styles kick in.

The fix is to regenerate Perfmatters’ critical CSS so it picks up your Customizer changes:

• In WP Admin → Perfmatters → Extras → Critical CSS — delete/regenerate the critical CSS for the front page
• Also clear the Used CSS cache specifically: Perfmatters → Tools → Clear Used CSS
• If you’re using the “Delay JavaScript” feature, make sure generatepress scripts aren’t being delayed in a way that compounds this

If Perfmatters has a “Remove Unused CSS” or “Used CSS” feature enabled, that front.used.css file needs rebuilding after every significant Customizer change. That’s your culprit.

As a quick test to confirm: disable Perfmatters temporarily — if the flash disappears, that’s your answer.

As far as the button is concerned: Regenerating the Used CSS should fix it cleanly without needing any additional overrides. Once you’ve done that, test logged-out in a fresh private/incognito window to confirm.