Substitute code partly working

Hello all. I have an interesting problem. I have the following code block in my spreadsheet. The first 'With' section works every time. The second 'With' section only works if I step through the code manually using F8. If I run the the entire macro using the Process button, it seems like the second 'With' block is just skipped alltogether. I tried commenting out the first 'With' block and when the Process button is pressed, the second 'With' section still seems to be skipped. I have attached a copy of the workbook. Can someone help fix this?

With Sheets("Class Roster Template")
    For Each rng In .UsedRange
        rng = WorksheetFunction.Substitute(rng, "/", "")
    Next rng
End With

With Sheets("Class Roster Template")
For Each rng1 In Range("J2", Range("J2").End(xlDown))
        rng1 = WorksheetFunction.Substitute(rng1, "M", "L")
    Next rng1
End With

Thanks,
Andrew