Excel vba excessive run time, but no issues using step into - vba

Question

I have some code to delete duplicate rows while keeping the first instance the particular string appears.
When I step into the code to delete duplicates, the macro runs without a hitch. However, once I hit run macro, my excel freezes and stops responding. I'm not quite sure why...
If anyone could shed some light. That would be greatly appreciated. (Also I added a breakline to show where I attempt to run to).
Sub CleanUp()
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
Dim lastRow As Integer
Dim i As Integer, j As Integer, k As Integer
Dim stakedItem As String
Dim sortCell As Range, allCell As Range, sortcell2 As Range
Dim currentItem As String, baseItem As String
lastRow = Sheet2.Range("A" & Sheet2.Rows.Count).End(xlUp).Row
Set sortCell = Sheet2.Range("A1")
Set sortcell2 = Sheet2.Range("B1")
Set allCell = Sheet2.Range("A1:Z" & lastRow + 1)
baseItem = Sheet2.Range("B2")
allCell.Sort key1:=sortcell2, order1:=xlAscending, Header:=xlYes
For i = 3 To lastRow
currentItem = Sheet2.Range("B" & i)
If currentItem = baseItem Then
Sheet2.Rows(i).Delete
i = i - 1
lastRow = lastRow - 1
Else
baseItem = Sheet2.Range("B" & i)
End If
Next i
Breakline here...
allCell.AutoFilter field:=2, Criteria1:=Array("*G*", "*HUB*"), Operator:=xlFilterValues
allCell.Sort key1:=sortCell, order1:=xlAscending, Header:=xlYes
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
End Sub
Thank you!
Francis

Answer 1

This will never exit if it finds a row to delete. The reason is that in a For loop, the exit condition is fixed when that line of code evaluates. That means lastRow will always be whatever it was when you entered the loop.
This code illustrates:
Sub example()
Dim x As Long, i As Long
x = 5
For i = 1 To x
Debug.Print i 'This runs 5 times...
x = 1 '...even though you change x here.
Next
End Sub
So, the only thing lastRow = lastRow - 1 does is decrement the variable. After you've deleted the first row, you're guaranteed that at the end of the sheet that currentItem = BaseItem. And inside that condition, you decrement the loop counter, which gives you an infinite loop.
As #TimWilliams mentions in the comments, you should loop backward if you are deleting rows. Something like this:
For i = lastRow To 3 Step -1
currentItem = Sheet2.Range("B" & i)
If currentItem = BaseItem Then
Sheet2.Rows(i).Delete
Else
BaseItem = Sheet2.Range("B" & i)
End If
Next i