Are you pulling the data with a Sub Report? If so check your subreport links to be sure that you are matching up the Invoice Number.
ex. on one of mine I pull in the payment info so the link fields say ?pm-Invchead.InovoiceNum > CashDtl.InvoiceNum
Also when printing groups I ran across an issue with Totals not resetting so I added a hidden Formula field with WhilePrintingRecords;
shared NumberVar variableName:=0;