Just an addition to what @BruceWayne already said: whenever you have this typical phenomenon that something happens only "sometimes" it is often a case of using keywords such as Active or Current or Selection. These are not specific but change each time that you call the macro. Whatever you have selected is the starting point. You might even start clicking around and thus change Selection while the macro is running. In short, you should start coding explicitly and don't allow VBA / Excel to assume / make the decision for you.
Let's start with Range("J14").Select. This line of code asks VBA to make already two assumptions:
- If you have several Excel files open. Which Excel file should it start with?
- Within the file there might be several sheets. On which of these sheets should
J14 be selected?
Explicit coding means that you (hopefully at all times) be very specific what you are referring to. So, instead of just stating Range("J14") you should use:
ThisWorkbook.Worksheets("SheetNameYouWantToReferTo").Range("J14")
But is pointed out in the other answer, this is not even necessary in this case. Rather loop the rows as shown and use:
ThisWorkbook.Worksheets("SheetNameYouWantToReferTo").Cells(i, 10).Offset(6, 0).Formula = ThisWorkbook.Worksheets("SheetNameYouWantToReferTo").Cells(i, 10).Offset(i, 10).Formula
Since this is a bit lengthy you can shorting it by using a With statement:
With ThisWorkbook.Worksheets("SheetNameYouWantToReferTo")
.Cells(i, 10).Offset(6, 0).Formula = .Cells(i, 10).Formula
End With