This has been happening at least the past month, if not longer. (for my searches)

When doing a search using the Find Lower Fare +/- 3 days option, the search will provide a lower priced flight on a different day. If you click it brings you to the spreadsheet type deal and from there you can pick the date that suits your needs. Upon clicking said lowest price, it is not that price that you just clicked on, but a much higher price that is about the same as the first.