Can not purge close noparent WFERROR (SR3-9723815191)

Hi Experts

In my customer instance, The CLOSED NOPARENT WFERROR can not be purged.

I have confirmed below

WFERROR CLOSED NOPARENT 4012792

Also confirm by select wf_purge.GetPurgeableCount('WFERROR') from dual; the almost same result.

But tried the following method, they can not be purged.

1. Run "Purge Workflow Obsolete Runtime Data Concurrent Program"
2. The API WF_PURGE.ITEMS('WFERROR',wf.item_key,SYSDATE,TRUE,TRUE);

Can anyone advice any other way to purge the items?

Any update is very appreciated.

Thanks & Regards

Andy Wang