Elastic Beanstalk stopped forwarding Docker logs

Our app is running in a Docker container on a EC2 instance over Elastic Beanstalk. Through .ebextensions we have set up an agent to forward the logs in /var/log/ to an external service. Yesterday we noticed a drop of the count of log messages. First we expected that the forwarder does not work as expected, but it was running without problems.

We made a ssh connection on the EC2 instance and looked into the files. We noticed that the file under /var/log/eb-docker/container/eb-current-app/ is incomplete. Normally we have about 1000 lines per minute, but now we have sometimes only 1 or 2 log lines although the app is running fine. Then we executed the docker logs command which shows all the logs.

I'm am a bit puzzled now why the docker logs are not written to the eb log directory. Our setup worked for years, but suddenly has stopped working. A workaround is to restart the eb app server, but as this has happened two days in a row, this is not a real help.