Google PageSpeed ??Insight: first it slows down and then it

Good morning everyone! I’m having a really strange problem with one of my client’s sites

Everything is up to date, uses the DIVI theme.

For a few weeks it has had a very strange conflict with the WP Reviews Slider Pro plugin (I’m also notifying its developer)

Basically what happens is that:
I clear the cache completely (Tools > Empty the entire cache), wait about 1 minute, and performance is top: https://pagespeed.web.dev/analysis/https-www-disintop-it/4qq69l02m1?hl=it&form_factor=mobile

A few hours pass and the performance drops: https://pagespeed.web.dev/analysis/https-www-disintop-it/bllq82hasf?form_factor=mobile

And finally, after a not always defined period, the scan goes totally wrong:

I found that the problem SEEMED to be the css of the above plugin (plugins/wp-review-slider-pro/public/css/wprevpro_w3_min.css), I tried putting it in the exclusions, generating a stand-alone critical CSS code, etc… nothing works in a ‘swinging’ manner

Help please!

Numero del rapporto:?XQWSOQQW

Data del rapporto: 11/18/2024 08:58:02

The page I need help with: [log in to see the link]