Why are you sure about the quality of the primers when this data is telling you that the primers are likely bad? Have you run the product on a gel to see if a clean band is obtained? You could try running gradient PCRs to optimise the annealing temperature to see if it's possible to clean up this primer set but it may be necessary to redesign the primers. Do you have any other primer sets that are giving you the expected results during the melting analysis?

Looks like you have minimal amplification of your target locus. What is the Ct value for that sample?

Do all of your peaks look like that one? If yes, then you need to optimize the reaction conditions and/or design new primers.