EDIT: this issue now tracks using installabilityErrors entirely to power the installable section of Lighthouse PWA. more details here: #10515 (comment)

original OP comment below;

https://code.nasa.gov/

Maybe related to how the page causes a PROTOCOL_TIMEOUT?

From https://bugs.chromium.org/p/chromium/issues/detail?id=951684