I’m trying to diagnose an issue with the Core Web Vitals measurement Cumulative Layout Shift (CLS)
– all 200+ URLs failed in GSC for both mobile and desktop.
When running the URLs in Pagespeed Insights, under the “Lab Data” header you can see the snapshots of the screen loading. Looking at this for mobile, the header/navigation is double-height for the majority of the load. It’s not until the final screen when the header halves in height to become the correct height.