Intermittent jumps/increases in consumer lag

Hi,

we're using the latest master build (at the time of this writing: https://github.com/linkedin/Burrow/commit/12e681a3a8a61f84f17677996dc3e6a2b79fac41)
Our Kafka-Brokers are running 1.1.0
We switched recently from https://github.com/Morningstar/kafka-offset-monitor to Burrow, because we're adding authorization to our Clusters.

Now, most of our consumer-lags are 0 most of the time (according to Burrow, whereas on kafka-offset-monitor they were around 1K - 100K most of the time - both are OK from our point of view).
For reasons unknown to us, the consumer lag "jumps" e.g. from 0 to 1.4 Billion(!) from one minute to the next, and back again after another minute. We have about 20 consumers on our main topic, and all of their lags jump - but by different amounts. Some "only" jump from 1k to 1M, others from 0 to the billions described above.

Is anybody else seeing this?
Is there a known reason or do we have to adjust our config? - We didn't change anything about the default config for the evaluation or notifications...

We use https://github.com/rgannu/burrow-graphite to report to graphite, and our alarming system is based on those metrics...

Any help is appreciated

Start by reproducing the intermittent lag jumps with Burrow's referenced master build, Kafka 1.1.0, the default configuration, and the burrow-graphite reporting path. Compare Burrow's reported consumer lag with kafka-offset-monitor and determine the cause or required configuration change; done means the reported metrics remain accurate and stable.