VBA buttons for hide/unhide rows disappear at random

Sorry about that. I edited the first post to include the correct code.

To answer your question: no, the buttons are all in rows that are unaffected by the macro. Their disappearance seems random. Regardless of which button is clicked, sometimes they all disappear, sometimes just a few disappear, and sometimes none disappear.

There is other code in the document, but I have the same problem whether or not I use this other macro. I'm using a ThisWorkbook macro to protect the document because hide/unhide rows will not work with Excel's built-in protection. Here's the code I use for this:

Private Sub Workbook_Open()
With Worksheets("Sheet1")
       .Protect Password:="password", Userinterfaceonly:=True
       .EnableOutlining = True
End With
End Sub

Also, I should mention that I'm not interested in a patch to fix my copy of Excel. This document is meant to go to several people, and I can't expect all of them to repair their software as well.