duplicate primary addresses causes error in report

The contribution and membership details report contained an error wherein the total was based on more rows than were presented in the report. Here's the summary at the end of the report:

Row(s) Listed 41
Total Amount $ 1,320.00(44)
Average $ 30.00

The report actually contains 41 rows and the total membership contributions for those 41 is less than the $1,320.00 reported in the summary.

I traced the problem to a few contacts that somehow possessed two rows in civicrm_address where is_primary = 1. Once this was fixed the report was correct and consistent.

I do not yet know how two addresses ended up as being primary for the same contact, but our principal user thinks it may be related to merging duplicate contact records, although I was not able to replicate the error in followup testing.

While the ultimate source for the multiple is_primary problem remains undetermined, the report itself should be consistent such that the detail records are based on the same rows as the total.