This sort of thing occurs when there is phantom data in cells not used for the merge (maybe a space that is difficult to spot). The following Excel macro should enable you to clean up the worksheet to avoid the problem. Certainly it fixes the problem on the example sheet you provided.
Code:
Option Explicit
Sub CleanSheet()
Dim xlSheet As Object
Dim iCols As Long, iCol As Long, c As Long
Dim iRows As Long, iRow As Long, r As Long
Set xlSheet = ActiveSheet
iRows = xlSheet.UsedRange.Rows.Count
iCols = xlSheet.UsedRange.Columns.Count
iRow = xlSheet.Cells(xlSheet.Rows.Count, 1).End(-4162).Row
iCol = xlSheet.Cells(1, xlSheet.Columns.Count).End(-4159).Column
If iRows > iRow Then
For r = iRows To iRow + 1 Step -1
xlSheet.Rows(r).EntireRow.Delete
DoEvents
Next r
End If
If iCols > iCol Then
For c = iCols To iCol + 1 Step -1
xlSheet.Columns(c).EntireColumn.Delete
DoEvents
Next c
End If
Set xlSheet = Nothing
lbl_Exit:
Exit Sub
End Sub