SPO - Document Viewer - Icons not showing

Dear all,

we have a problem with the Document Viewer in SharePoint Online, since these days it doesn't show all Icons in the Command bar:

Seems like the :before is missing in the I tag:

When i take a look on the Search Icon there is a :before available with the Icon as it's content.

Did i missed something? Are we the only one who have this problem?

Thanks, Patrick