Range.Offset produces incorrect cell address

Hi

In producing a fairly involved solution to this question Need Help Improving/increase Speed of ChangeTracking Macro, I noticed a strange problem (or made a mistake I can't see!).

In looping through two 2D arrays (and writing to a third) using counters m (effectively 1 to 25) and n (effectively 1 to 10) , I get a problem only when n is 4 (which is row 9  of the TDatas sheet in the file provided for that question). The code writes one of the values to the third array using the line:

ChngArr(r, 2) = .Cells(m, n).Offset(5, 1).Address

but with m= 4 and n=9 (say), it records $Z$9 (and the same for n values other than 1).

If however (with that sheet active) I check in the VB Project Explorer's Intermediate window, I get the correct result, J9 using:

Debug.Print Cells(4, 9).Offset(5, 1).Address
$J$9

The same happens when m=4 (only) with three later lines like:

Select Case CurrArr(m, n)
                Case Is > PrevArr(m, n)
                    .Cells(m, n).Offset(5, 27).Interior.ColorIndex = 4 'green

but with the changed offset, it applies the colour to cell AB9 correctly (n=1) but to AZ9 (rather than cells AC9:AY9 successively when n>1).

Any ideas?