I noticed that the console output for (at least) wmf-quibble-vendor-mysql-hhvm-docker is quite messy. For instance, here the "setup-quibble-npm-ls" header is repeated multiple times instead of simply showing the test error.

Here, instead, no error is shown (although the build failed) and clicking on "Show Details" in the last section does nothing; for this one, the plain text output reveals where the problem is anyway. It also logs the following in browser console:

script.js:13 Uncaught TypeError: Cannot read property 'className' of null
    at doToggle (script.js:13)
    at HTMLParagraphElement.onclick (console:790)