Fix the issue of product app (Flutter or kotlin)

Hi, we are looking someone has skills and used before below technologies.We want you to find the issue of project and fix that issue as professional. Also, we do not want pay you until find the issue.if you find the issue you will give us estimated time or fixed price so we can discuss more! We can share the sample project also with you and you can test on your side too.The project is mobile app and we used below technologies for the backend of the project.We are thinking the problem regarding socketio. Please do not ping if you are not familiar below technologies.

1)Nest js
2)Typescript
3)Redis
4)Socketio
5)Node.js
6)Mongodb
7)Docker
8)Fronted(Flutter or Kotlin)

We have a some issue about app functionality if you are familiar with those technologies we can discuss more details.
Note: the fixed price just for sample.