A user runs a report and finds some hits. Then the user clicks Download All Results to generate a CSV file. Upon opening the CSV file the user sees a lot of unwanted rows/data in it.
This is a known issue in versions 16.4.2 (Defect 763670 refers). The error is caused by a wildcard character (% or *) being used as the default search criteria in one of the search parameters.
The solution will be provided either as a hotfix in version 16.4.2, or be fixed and included in a future general release.
Run Director, locate the report and then open Report Designer. Under the Report Parameters tab remove the % or * character in the Search Parameter field. Just leave the default value field blank. Then save the report.