Right have spent all day looking at this!

I have found a fix for it and its basically setting various properties on the editor in the right place and order! In a nutshell I had to set

Protected Sub form1_Init(sender As Object, e As EventArgs) Handles form1.Init   Editor1.AllowScriptCode = True   Editor1.EditCompleteDocument = True   Editor1.TagBlackList = ""
End Sub
 

I don't normally use form_init, I usually do things once in page_load if not page.ispostback.

Protected Sub form1_Load(sender As Object, e As EventArgs) Handles form1.Load
  If Not Page.IsPostBack Then
   Editor1.AllowScriptCode = True  Editor1.EditCompleteDocument = True  Editor1.TagBlackList = ""    Using objRdr As System.Data.SqlClient.SqlDataReader = SiteDB.SiteSelectPageHTML(881)
      If objRdr.Read() Then
        If objRdr("DocTypeDTDID") = Globals.DTDTypes.HTML4_01Trans Then
          Editor1.DesignDocType = RTE.RTEDesignDocType.HTML4
        ElseIf objRdr("DocTypeDTDID") = Globals.DTDTypes.XHTML1_0Trans Then
          Editor1.DesignDocType = RTE.RTEDesignDocType.XHTML
        Else
          Editor1.DesignDocType = RTE.RTEDesignDocType.HTML5
        End If
        Editor1.Text = objRdr("HTML")
      End If
    End Using
  End If
End Sub 

However doing it here only works when you set the text, the settings seem to have been forgotten on the return postback, it seems you have to set them in init everytime whether its the first time the page is loading or being posted back. I also found I had to set them before I set the text property. This all worked in the old version, so was sort of expecting this to work in the same way.

I do think its a bug in that it forgets you set the settings

  Editor1.AllowScriptCode = True   Editor1.EditCompleteDocument = True
  Editor1.TagBlackList = ""