TTFB of "-" for Repeat View

[mickined]

I am trying to figure out what's happening on repeat views for this test Firebase site:
https://webpagetest.org/result/200208_Q6...2fd24c38d/
https://webpagetest.org/result/200208_5A...9a6772c44/

In particular, why is the First Byte time "-" on the Repeat Views? This happens consistently on different test scenarios.

Note that one of the tests above returned a 404 on Repeat View, but the other (and most) tests did not.

Thanks!