Executing playbooks from callback, It became slow all of sudden,

I am using the below function for the past 4 months to orchestrate the installations/depolyments and it was quick.

It was working fine and all of a sudden, it became dead slow. I do not remember tweaking settings.

def run_playbook(listVMs, playbook, user, extra_vars=None, key_file=None):
print(datetime.datetime.now())
stats = callbacks.AggregateStats()
playbook_cb = callbacks.PlaybookCallbacks(verbose=utils.VERBOSITY)
runner_cb = callbacks.PlaybookRunnerCallbacks(stats, verbose=utils.VERBOSITY)

pb = ansible.playbook.PlayBook(
host_list=listVMs,
playbook=playbook,
forks=20,
remote_user=user,
remote_pass=‘centos’,
runner_callbacks=runner_cb,
callbacks=playbook_cb,
stats=stats,
extra_vars=extra_vars
)

pb.run()

run_playbook(listAllVms, ‘./resources/yaml/playbooks/all/config/yumbootstrap.yml’, ‘root’)

Please help.

And regular: ansible-playbook command works fine when the playbook is pointed.