File Viewer web part does not handle Word documents when they are in a one-third page section

Using a File Viewer Web Parts in a SharePoint Online modern site I found that a .DOCX file would not display correctly when configured in a small (i.e. one-third) of the page section. Specifically, the document showed up but with no download or open controls . Other file types (e.g. .PDF, .PPT or .WMV) all worked perfectly.

The File Viewer and .DOC worked perfectly, though, when in a larger page section (half-page or full-page).

The attached image shows the problem: I used the same .DOCX file, each in a File Viewer web part. The  only difference is the size of the  section. Note that below the larger section, you can see the controls that support download etc. The same controls are not displayed or accessible in the smaller section.

Any ideas?