502 bad gateway on authorize kea machine, but it is visible in authorized machines after

This issue happened to me while running stork demo.

I tried to authorize 2 kea machines: agent-kea6 and agent-kea. The latter couldn't be authorized, I got 502 error.

Request:

XHRPUT
http://127.0.0.1:8080/api/machines/8
[HTTP/1.1 502 Bad Gateway 280ms]

{"address":"agent-kea","agentPort":8888,"agentToken":"(...)","apps":[],"id":8,"authorized":true}

But the machine disappeared from unauthorized machines and appeared in authorized:

I also got some 502's and 504's in console after: