What component should I add here?

now it is up.
This down-up, down-up happened in the last 15 minutes.

I'm not seeing anything very suspicious on our statsd dashboard (not posting link here because it's not a very robust host).

I got this error just now

Error. Server Error
Therefore we served HTTP status code 502.
The server encountered a temporary error and could not complete your request.
Please try again in 30 seconds.
This is likely because the application is down. If you are just a user and not interested in the technical details of this error, please reach out to TechStop.
Otherwise, for additional troubleshooting please see go/uberproxy-502
Do not take a screenshot of this page, rather copy/paste the text. You will be asked for the text.
host: cautotest.corp.google.com
time: 2016-05-19 13:10:35
Please see goto/uberproxy-error-codes for error details

Comment #6 issue seems like a separate problem.

Filed  issue 613284  for #6, Removing the bulky comment.

Additional info - at the time cautotest is down, the 'atest' command was stalled.

Autotest is now working for me

For me too.