SharePoint Search not returning custom list items (modern experience)

This is a confusing issue, and I cross my fingers for some assistance :-).

In my SharePoint-site I have a custom Issues-list with two items:

1. Issue 1

2. Issue 2

Scenario 1:

In the list view, I search the list with keywords like 'Issue' and 'Issue 1'. Items show up as expected. 

Scenario 2:

I use the same search keywords at the default start page and nothing appears in the search results.

I figured that the items might not be indexed, so I checked the list settings. The settings were fine - items will be shown in the search results. Then I switched to classic experience and provided the same keywords, and voila! - the list items were displayed (osssearchresults.aspx).

Can anyone explain to me how the search box at the default start page is supposed to work in the modern experience? Shouldn't the search results be exactly the same as in classic mode?

Regards,

Margareta