I have written a formula in excel:
=SUMPRODUCT(('Gross PAYM Talkplan Data'!$G$3:$G$3973=CH$119)*('Gross PAYM
Talkplan Data'!$J$3:$J$3973=$A124&"P"&"18 month"),('Gross PAYM Talkplan
Data'!$E$3:$E$3973))

In the data it is looking at, 1 of the criteria to pick up the correct
numbers is either "P" or "SB" depending on what I'm looking at.
In most instances, the above formula is bringing back only results with a P,
but in some it's bringing back the results for both P & SB so my figures are
wrong.

The formula has been copied across & down in my table so there's no
differences except for which column/row (CH$119/$A124) it looks at.

Why is it doing this & how can I stop it?

Thanks
Miranda