Thanks for your question, and for following up with the update, @Globalteahut. What you are experiencing does make sense, and actually is expected behaviour! Let me explain.
Reports capture the details of an order at the time of the sale. Therefore, if you change any product details, such as assigning a new vendor to an existing product, then both the original product details and the new details appear in a report.
So for your situation, since your products were associated with the old vendor at the time they were sold, pulling a Percent of inventory sold report for the date range during which the old vendor name was used will still associate those products with that vendor. Moving forward, your Percent of inventory sold report will show the same product twice (once for each vendor) when the date range spans from before and after the change was made. Does that make sense?
There’s more of an explanation of this in the section titled Changes to product details in our Sales reports Help Doc. Let me know if this helps!
My pleasure, @Globalteahut! I’m happy it was helpful. Let me know if you have any other questions or concerns.