WhilePrintingRecords summary forumula problem

Hello

I have used the WhilePrintingRecords function (full formula below) on a number of reports in order to create a sum of a field which appears in the group footer. In order for the field to work properly it needs to be included at the group level and report footer level. It is working correctly on a number of reports but on one report the 'total' value in the report footer is 1 higher than the incremental count on the last group footer. In my investigations I removed the field from the group footer and the value on the field in the report footer is '1' (it should be '0'). If I do this on one of the reports that works, the value in the report footer is '0' which is correct.

Would anyone be able to provide assistance or shed light on what may be happening to produce this erroneous value?

Many thanks in advance

WhilePrintingRecords;

NumberVar Report_Summary_Field:=Report_Summary_Field + {@formula field};