Is the issue just execution_timeout set to a low value? For me it was giving the zombie error but setting a higher value for execution_timeout solved it.

from datetime import timedelta

create_plots_task = PythonOperator(
    task_id='create_plots',
    python_callable=create_plots,
    provide_context=True,
    execution_timeout = = timedelta(minutes=120)
    dag=dag,
)