Authentication API intermittent failure

We are using a free account for testing purposes. Our login API is failing intermittently. After failure it redirects the user back to our website with a failure response.

We suspect that this has nothing to do with us reaching our quota limits. We use the same auth0 account on two servers. And there were times when it was failing on one server but working on another server.

Below are logs from auth0 console for some our failures:

{
  "date": "2019-09-16T06:27:26.551Z",
  "type": "fcoa",
  "description": "Unknown or invalid login ticket.",
  "connection_id": "",
  "ip": "<hidden>",
  "user_agent": "Chrome 76.0.3809 / Mac OS X 10.14.5",
}

{
  "date": "2019-09-12T12:59:46.466Z",
  "type": "fcoa",
  "description": "Unable to configure verification page.",
  "connection": null,
  "connection_id": "",
  "client_id": "<hidden>",
  "client_name": "<hidden>",
  "ip": "<hidden>",
  "user_agent": "Safari 12.1.0 / Mac OS X 10.14.4"
}

If anyone has faced something like this we will really appreciate the help.

FYI our login screens are hosted on our own servers.