The issue is reproducible with RadEditor. When using Lightweight rendering in RadEditor, the FileExplorer's address bar has an inline style with height: 16px rule. This rule should be added only in Classic rendering.

As a side effect, the text in the address box is cut off. 

Possible workaround is to add setting in the web.config to force Lightweight rendering for RadFileExplorer:

<add key="Telerik.Web.UI.FileExplorer.RenderMode" value="lightweight" />