It seems like the Jawbone API has a problem on one of its nodes. When calling the endpoints below sometimes requests succeed and sometimes fail with an "Service Unavailable" response. The requests are the same an I have tried the calls from different machines. Any one else experiencing the same problem?
Endpoints: https://jawbone.com/nudge/api/v.1.1/users/@me/moves https://jawbone.com/nudge/api/v.1.1/users/@me/workouts
The issue should be resolved now.
tl;dr: Some changes in routing resulted in malformed requests to the servers. The servers stopped responding, so nginx gave you a 503.
Original Answer:
The Jawbone partner API servers are suffering a minor outage. The team is looking into the issue. As you noted, it's not a complete downtime.
There is no ETA for resolution yet. I'll update this answer when I know more.