produceStrings method slow down on sending messages

Hello,
working on the Vert.x Kafka client which uses Debezium provided Kafka server/cluster for unit tests I noticed the following behaviour.
I updated Vert.x Kafka client project to use Kafka Client 0.11.0.1 and Debezium 0.6.2.
The following test fails due to timeout.

https://github.com/vert-x3/vertx-kafka-client/blob/master/src/test/java/io/vertx/kafka/client/tests/ConsumerTestBase.java#L361

It seems that using the 0.6.2 version, the produceStrings isn't able to send 5000 messages in 10000 msecs anymore.
The same test works fine using Debezium 0.6.1 and using previous 0.5.1 with Kafka client 0.10.2.0.

Thanks,
Paolo