Search Button for Memo Field, overflow error

Experts,

I get this overflow error sometimes in the code below.  
The search term is actually contained in the memo field but it returns the error (attached).  

this is a follow up to a question:
https://www.experts-exchange.com/questions/26481808/Find-button-for-memofield-txt-box.html

How can I get rid of the error? (note that the search term is in the memo field but still gives error...sometimes though).  

Maybe someone can give me different code options for this search in a memo field that is rich text.  It doesnt seem to be very predictable and doesnt pinpoint the item found.  It si usually way off and highlights another term and not the search term.  If I change the setting from rich text to plain text then it works fine and search term is pinpointed exactly.
thanks..

Private Sub cmdFindWord_Click()

  sWord = InputBox("Type word to find")
If Len(Trim(sWord)) > 0 Then

    sNote = Me.txtNotes
   
    'j = InStr(sNote, sWord)
    j = InStr(PlainText(sNote), sWord)
   
End If
If j <> 0 Then
   
    Me.txtNotes.SetFocus
    Me.txtNotes.SelStart = j - 1
    Me.txtNotes.SelLength = Len(sWord)
    Else
    MsgBox "Word " & Chr(34) & sWord & Chr(34) & " not found!", vbQuestion, "WORD SEARCH"
End If



End Sub

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