Cached AMP pages break on WPT lighthouse test

Support
1

Running WPT against pages in the Google AMP cache. We use a private instance of WPT. Our tests started failing on 26th July.

this is an example page we test against:
https://www-babycenter-com.cdn.ampproject.org/c/s/www.babycenter.com/amp/0_signs-of-labor_181.bc

I’ve attached a screen shot of the results I get on our private instance

I also ran a test on public WPT and got slightly different but still bad results
https://www.webpagetest.org/lighthouse.php?test=190805_92_e4580833ddd1a540e9d3ce9689c47246&run=1

The page is fine and the regular WPT tool gives normal results.

thanks in advance for any help

[attachment=905]

2

A bit more information. The breakage of the Lighthouse tests against Cached AMP pages started when our private instance of WPT started to use Lighthouse 5.2.0

3

More investigation it seems this is an issue with lighthouse 5.2.0 that others have seen.
https://github.com/GoogleChrome/lighthouse/issues/9562

A PR is here which may fix it.
https://github.com/GoogleChrome/lighthouse/pull/9576