The error message that occurs when testing with Lighthouse, which causes a drop of 8 points in the SEO metric, "robots.txt is not valid - Lighthouse could not download robots.txt file", is a common problem when using a network for content delivery (CDN) such as Cloudflare.
This supplement in robots txt, I mentioned eliminates this issue. Probably Lighthouse changed (updated) their version and introduced a bug.
Another issue related to the SEO metric is that 2 zones are indicated in a guest cookie message, for poorly sized tap and click zones. And when viewing these areas, they are not links to touch, but part of the text - which is also a consequence of this bug.
Add-on in robots txt removes and this issue.