We’ve duplicated the issue. When reports are added, we calculate a unique signature for each report. When you make a change to the report, such as with the Change Data Source tool, the report’s unique signature changes. It appears that due to a bug, it’s not updating that signature after the Change Data Source tool is run on an existing report. So when you add the report again, even though you have it set to overwrite, since the signatures differ .rpt Inspector Online is treating it as a newly added report instead.
We’re working on a fix and will let you know once it’s available.
BTW, on a report(s) that were added to .rpt Inspector Online, if you then make a change to them outside of .rpt Inspector, since the signatures will now differ, when you add the report with overwrite, you will still get two of the same report(s). This is by design, so you’ll want to first remove such reports, or remove them after the add with overwrite.