I use custom code to sum a Total of group Totals. I also call a reset function in the report header to keep the variable to increase with every call of the report.
This works as expectet, but the Totals also reset on changing the visibility of groups. So if I open a detail group the Totals are change to Zero. If I change the filter of the report the Totals are back untill i open a group and the function reset the totals to Zero.