Context menu icon (hamburger) missing in reports of type List

In reports of type List, the context menu icon (hamburger) is not visible, but right-clicking on the context menu works correctly.

1. Navigate to Reports > View /Run.

2. Open any Report of list type, for example, Active Change Requests
(https://<instance_name>.service-now.com/nav_to.do?uri=/sys_report_template.do%3Fjvar_report_id%3Da1849841c611227b01646de563508c09).

Note that the contextual menu (hamburger) icons that should be visible in front of each column name are missing, but right0clicking the header works correctly.

Access the information by right-clicking on the context menu.