It is nice you have found a solution for your problem, though I don't quite understand it. You are saying that you drag and drop "files" to the page group. Perhaps you mean controls?
Anyway, I think there is a faster way to achieve these though it is less reliable. You could directly change the type of the control in the database. All you need to do is run this script:
SET type = 'Telerik.Cms.Web.UI.Breadcrumb, Telerik.Cms.Web.UI'
WHERE type = 'Telerik.Web.UI.Breadcrumb, Telerik.Web.UI'
Please backup the database in case something gets messed up. Hope this fixes your problem faster. Let me know how it goes.
the Telerik team