Amzon EMR - Solve a bug

In an EMR cluster - running a pyspark job works fine from the command line but fail when running from an EMR-step.
Details

SSH into the EMR master and running my pyspark job using spark-submit - it works fin on all executors.
When running the same job using an EMR-step (and a jar running spark-sbumit) - the job only runs on the driver.

If you think you can help - please let me know.