VERIFIED SOLUTION i
When performing a 'Search For Task' using the SearchForTask3 Data Access Transaction (DAT) configuration node, and certain combinations of search criteria cause an Access Violation (which can be seen in the Event Log), a Dump file is generated at Foundation's install location.
There is a known problem with some of the error handling code within this Data Access Transaction. The issue is normally caused by corrupt or incorrectly configured workflow instance data, but this is made much worse by the fact that the primary HostU service crashes due to a bug in the error handler.
ResolutionUPDATED: April 4, 2017
If you see this issue in your testing, contact Support and request a patch for "Portrait Foundation Workflow SearchForTask3 throws an Access Violation under certain data circumstances" quoting reference 'TFS-33402'