These are dashboards which are scheduled to be emailed out at 8am every morning. The dashboard widgets contain data from the previous 24 hours. Occasionally, certain panels in the emailed report will show "No results found.". If I go to the dashboard immediately after it is emailed out and this message is displayed, the results are populated within seconds, no problem.
It seems for some reason the results are not making it to the report. Again: within seconds of the emailed report being sent out with the "No results found", the dashboard can be run manually and the results will populate quickly. So it appears the results are available at the time of report generation. It is not always the same panel that displays "No results found".