I just rolled out a big update of my main website. It is completely revamped from A-Z.

But when I run the pages through Fetch and Render, they do not render correctly, The menu along the top of the screen expands over the full screen. This is the case for both desktop and mobile. The fetch portion of the tool displays the source doe correctly. Page Speed insights also is unable to test the speed, it gives me good score for optimization but is unable to test the speed.

Testing in an actual browser shows everything works as expected. I tested, Chrome, Opera, Firefox, Safari and I have found no issues.
The website is live and has been running fine for the past three days, the user metrics do not suggest any issues.
The pages pass w3 validation (except for errors related AMP)
Chrome Lighthouse also shows everything is working correctly.

I am worried that there is some small technical issue or oversight that is going to cause me a disproportionately large impact in terms of indexing/rankings.

Need I be worried? Any ideas on what the issue might be?