How did you conclude, that workflow is in failure state? Did you review a workflow execution history, step-by-step and you could point an error? For a not a transient workflow, the status is a value of "status" property in workflow instance node, example:
/var/workflow/instances/server0/2019-05-19_2/myworkflow@status.
If you are certain that it's failed workflow, you can set the status via CRXDe. In a case AEM still marks a failed workflow as running, I suggest opening a Daycare case