AOW Workflok not working fine

Hello guys,

Am using suitecrm 7.6.4 version, am facing issue in workflow module when a workflow execute more then one record they not executed and status of second record reflected “Running” and in job_queue table job status was “fail” and reson was “Unexpected failure, please check PHP logs and suitecrm.log” and in .log file nothing explain the issue kindly help