The compiler bypass some value, when tring to use find function

I have the following code:

Set rngFindValue = Sheet1.Range("A1:A13").Find(Sheet2.Range("A" & i), , xlValues)

The problem is that when the value is: 1, 11, or 4, the compiler bypass that field. It is ok with other value upto 13. I guess there should be better phrase that will help me avoid that conflict other than this phrase: Sheet2.Range("A" & i)
Can anyone help me comeover this issue?

The full code:

Dim Loop_Source As Range: Set Loop_Source = Sheet2.Range("A1:A13")
Dim strFirstAddress As String
Dim searchlast As Range
Dim search As Range
Dim rngFindValue As Range
Dim i As Integer
For i = 1 To 13
Sheet1.Range("A1").Activate
Set rngFindValue = Sheet1.Range("A1:A13").Find(Sheet2.Range("A" & i), , xlValues)
  Sheet2.Range("B" & i).Copy Sheet1.Range("B" & rngFindValue.Row)
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