I'm betting that you do have lots of invisible Commandbuttons on that sheet--but
they're hidden.
If you show the control toolbox toolbar and click the design mode icon, do any
appear on that worksheet?
You could delete them manually if you could see them. But if they're really
small or scattered, it could take a longggggg time.
Instead, how about a macro?
You could delete the hidden ones or even show them:
Option Explicit
Sub testme()
Dim OLEObj As OLEObject
Dim wks As Worksheet
Dim HowMany As Long
Set wks = ActiveSheet
HowMany = 0
For Each OLEObj In wks.OLEObjects
If TypeOf OLEObj.Object Is MSForms.CommandButton Then
If OLEObj.Visible = False Then
HowMany = HowMany + 1
OLEObj.Delete 'oleobj.visible = true 'if you want to see them
End If
End If
Next OLEObj
MsgBox HowMany
End Sub