I agree that you should take it in and see if you can get to the bottom of the problem. The shop staff will have an opportunity to exhibit good customer service. If you approach them with "Can you help me?", I think you can expect that they will do their best to solve the problem.
I purchased a generic walking foot for my vintage Pfaff machine from a sewing machine repair shop. It was lopsided, and it was a fight to sew a straight seam with it. The shop owner agreed with me that it was defective and took it back. She found another brand and told me to take it and try it out. If it worked, I was to come back and pay for it, which I did.
A good shop wants a satisfied customer, and they will work with you to find a solution.
Dayle