Session: Error while trying to free lock for ci_session:guid.lock (3.0.6)

Recently moved to a load balanced environment on AWS, ElasticBeanstalk nodes and a Redis Elasticache server for sessions (no sticky sessions). This message appears in the logs very frequently. Previously the app used file based sessions since it was a single server. It doesn't appear to break anything but I'm concerned there's an issue somewhere I'm not familiar with.

Any idea what can cause this and how to fix it?