Hello,

My first guess is that the Javascript testing tool you've tried doesn't recognise arrow functions or template literals, and doesn't understand minified code. I'm confident all of that code is valid and isn't responsible for the delay in your screenshot.

Based on your screenshot, it seems like that page had a task which took a longer time than usual to finish, which potentially held up the Layout task from finishing. Do you constantly get that result, or was it a one time occurrence? I ran the same test on your site (and mine) with Slow 4G about 5 or 6 times and had consistent results, but very different ones to you (no slow tasks).

There doesn't seem to be an impact on your performance either, with multiple tests on your homepage scoring 97.

I just tried the default theme on my own development board, which scored 99. If you're able to constantly reproduce the issue, it might be worthwhile trying with the default theme, or removing any modifications which may have been applied.

If that still doesn't work, I can take another look, but if I still can't reproduce it on my end, it'll be quite tough to diagnose. I'm hoping this was just an unlucky page load.

Make and show 3 consecutive tests on mobile. Here you have shown desktop result.

I get this when I do consecutive tests every 8-10 minutes. Including with a dev tool. That is, after getting a good test result (88-94 for mobile) - the next few tests are with a fixed result of 67, rendering time twice as large as the actual time CSS, which is about 600ms) - and the reported time from the test is over 1300ms, without an indication of where the difference comes from. This suggests inline resources - and these 3 JS are. I do not use personal inline CSS in my theme.

I get such results when testing and this site here. I opened a topic about this back in beta8 - and since then there has been no change in these tests.

This also looks like a test of a cache guest page , because if I remove the cache site before the test, start manually clearcache and after it profilesync tasks - then the PSI test has very good indicators for mobile. But after 10 minutes of testing it drops to 67 points, and this continues for maybe an hour.

The same behavior is seen in tests with the Chrome Dev Tool - after an excellent performance test - the results follow as I have shown in the picture above...

PS. here is the result from this site/forums - inexplicably large render delay