Events displayed incorrectly in sidebar

In the left sidebar, under Navigation/Calendar, some events are incorrectly displayed at top level, same level as calendars'. E.g. in the screenshot attached, events that belong to the calendar Other Events are being displayed at the top level, while they should appear as child nodes of the menu item Other Events in the sidebar.

Note: I am thinking maybe events shouldn't be displayed in the sidebar at all, because if the team is large and many members put their events in calendars then the sidebar might become heavy and less useful.