Filter results are empty in dashboard gadget but not in the filter page

Problem

The filter results gadget doesn't show any results whereas the filter page (with the JQL) shows issues as expected.

Diagnosis

Change the JQL of the filter and see if the gadget displays the results correctly.

For instance, if the JQL has a date comparison like CreatedDate > 2018-12-11, remove the clause, save the filter and refresh the dashboard page.

Cause

The root cause of the problem is still unknown.

Workaround

1. Capture the filter results gadget configuration to replicate it.
2. Delete the gadget from the dashboard.
3. Add a new filter results gadget with the same configuration.