CA WA Agent may report "scan has failed" on file monitoring jobs. This usually happens when file monitoring or file watcher jobs are monitoring files on a remote location. The agent is unable to maintain constant connection to the remote file share and results in failed scan for the file it is monitoring. Although very rare, error may be reported due to very high local disk activity as well.
A simple workaround is to increase the poll interval between for file monitoring. By default, the interval is set to 30 seconds (30,000 milliseconds). The following parameter may be added/edited to the agentparm with a newer value.
filemonplugin.sleepperiod=<milliseconds>
E.g. One minute or 60000 milliseconds
filemonplugin.sleepperiod=60000
If the problem still persists, the network connection should be investigated for any congestion or other related problems.