I’ve received a few reports of GetCompetitivePricing calls not returning the correct BuyBox offer recently. What’s worse, is I’ve honestly not been able to reproduce the issue myself - every single case (including the ASIN Paul linked to above), the correct BuyBox price has been returned by the API call when I try it.
That said, a few sellers have opened MWS support cases with RequestIds illustrating the opposite, so I have continued to investigate. What I have determined is that MWS is sporadically receiving the wrong data from the backend store responsible for the BuyBox data. This is why we’ve had such trouble nailing it down - random failures are hard to trace.
If you are encountering this issue, please feel free to open a Contact Us to the MWS team, and include the RequestId and timestamp for the call. I can dig into the server logs to tell you whether a particular request was a legit response or one that received incorrect data.