Inconsistent performance on pagespeed

I have a site in production which is having heavy oscillation in performance seemingly at random. For example here is a scan with extremely good performance https://pagespeed.web.dev/analysis/https-codicerisparmio-it/k5gancc7ra?form_factor=mobile and a scan fresh of this morning https://pagespeed.web.dev/analysis/https-codicerisparmio-it/xl21vfq5ik?form_factor=mobile I tried practically everything: caching aggressively through redis, changing settings in cloudflare, tweaking mariadb config, optimizing the js and css and while this helped swinging the score toward the upper limit it still swings down heavily toward 60 at random. I ran various profilers but all I could gather was that the problem isn't the db since the queries are executed extremely fast.