This issue can be caused by the cache on the agents or by outdated Smart patterns. To resolve the issue:

Option 1: Purge the cache.

1. Unload the client.
2. Delete the cache.dat file from the ..\Trend Micro\Client Server Security Agent\ directory.
3. Reload the client.

Option 2: Make sure all the pattens are up-to-date, especially for Smart patterns.

1. Log on to the WFBS console.
2. Go to Updates > Manual.
3. Make sure Smart Scan Pattern and Smart Scan Agent Pattern are updated.
4. Perform updates from the WFBS agent to get the latest update from now on.