next-e-commerce | commerce website example with NextJS that I made in 1 week | Authentication library

Here is my situation. I am trying to set up a Next.js project with an Express.js back-end. I did set up the back-end as a regular one not as a custom server according to Next.js documentation. So I am not sure if I am already making a mistake by setting up the back-end as a regular one. I am trying to fetch data from a back-end endpoint http://localhost:3500/api/v1/list using axios and it works well. But when I am trying to implement React-Query on the first load I am getting the right data from the back-end but when it is trying to re-fetch for some reason it is hitting the wrong end-point http://localhost:3600/api/v1/list and getting the 404 Not Found error. It looks like it is switching the port from 3500 to 3600 which is a front-end port. Here you will find the link to the repository and here is the code. Let me know if I am doing something wrong,

page/sell.js