The value of Provider[Guid] is added to the href until the RadEditor content area is submitted, because the url has to be resolved. Make sure that the dynamic content is resolved - this is done in the built-in controls, but you should do it manually for the custom controls.
Just to let you know Telerik.Cms.Engine.WebControls.HtmlContentEditor is obsolete and it is no more in use.
All the best,
the Telerik team
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