Have you included search head captain in your search? I believe only the scheduler node will get the failed logs. If you have included them, follow my next steps.
Do you find them in your logs and they aren't extracted? Append the below SPL to extract them.
| rex field=_raw "status=(?<status>\w+)"
Do you get them when you do stats count on status?
If not then you have 100% success rate on the searches.
