Elasticsearch Loader unexpected exception

Having this in ES good event loader logs. Here’s my latest config:

source = kinesis

sink {
  good = elasticsearch
  bad = kinesis
}

enabled = good

aws {
  accessKey = iam
  secretKey = iam
}

kinesis {
  initialPosition = TRIM_HORIZON
  maxRecords = 10000
  region = eu-central-1
  appName = "snowplow-loader-good"
}

streams {
  inStreamName = enriched_good
  outStreamName = enriched_bad

  buffer {
    byteLimit = 5000000
    recordLimit = 1000
    timeLimit = 1000
  }
}

elasticsearch {
  client {
   endpoint = "127.0.0.1"
    port = "9200"
    maxTimeout = 10000
    ssl = false
  }

 aws {
    signing = false
    region = eu-central-1
  }

  cluster {
    name = db
    index = "<good-{now/d}>"
    clusterType = enriched_good
  }
}

Been experimenting with various buffer sizes, but still ended up with this exception. Running ES 6.2.2 cluster.
Weirdly, this started happening after my failed attempt to utilize amazon-kinesis-scaling-utils - it incorrectly scaled down my stream aggresively. Does anyone have any guidelines using this tool with snowplow realtime pipeline?

Also, what is a sensible buffer size for ES loader if I run let’s say 6 shard enrich stream. Do people run loaders and enrichers on separate ec2 instances and scale them according to shard count?

As in most times here, replying to myself in case anyone else runs into such issue.
We were running a fork from 0.10.0-rc2 and forking 0.10.1 stable instead seems to have fixed the issue.