Try this code see if it makes any difference:

Sub Sample()

Dim lastRow As Integer
Dim lRowCount As Integer, i As Integer, d As Date
Dim v As String
v = "1st_Run"

Application.ScreenUpdating = False

Sheets("Tgt").Range("B6:XFD1048576").Delete Shift:=xlUp


With ThisWorkbook
    lRowCount = Sheets("Src").Cells(Rows.Count, 1).End(xlUp).Row

    d = .Sheets("PROCESS").Range("F3").Value
    .Sheets("tgt").Range("B6").Resize(lRowCount - 1).Value = v
    .Sheets("tgt").Range("C6").Resize(lRowCount - 1).Value = d
    .Sheets("tgt").Range("D6").Resize(lRowCount - 1).Value = .Sheets("Src").Range("B2").Resize(lRowCount - 1).Value
    .Sheets("tgt").Range("F6").Resize(lRowCount - 1, 5).Value = .Sheets("Src").Range("C2").Resize(lRowCount - 1, 5).Value
    .Sheets("Tgt").Range("E6").Resize(lRowCount - 1).FormulaR1C1 = "=RC2&""|""&RC3&""|""&C4"
    
    For i = 2 To lRowCount
        .Sheets("tgt").Range("Z1").Value = 1.05 ^ (Month(d) - Month(CDate(.Sheets("Src").Cells(i, "A").Value)))
        .Sheets("tgt").Range("Z1").Copy
        .Sheets("tgt").Cells(4 + i, "F").Resize(, 5).PasteSpecial Paste:=xlPasteValues, Operation:=xlMultiply
    Next i
    .Sheets("tgt").Range("Z1").ClearContents
    .Sheets("tgt").Range("A1").Select
End With

Application.ScreenUpdating = True

End Sub