Mysterious Malfunctioning of a working project (probably due to custom fields)

We have built a React based custom app(basically a large form) and integrated it with jira.

It’s purpose is to give an alternate route (with additional features) to create an issue in a project.

When we delivered it to the client, it was working as intended. But after some client testing and probably with some changes on Jira side, we’re not able to create issues from custom app.

However, it’s possible to create an issue from the customer portal.

To check our code validity, we created a new service project in jira and changed the serviceDeskId and RequestId to the new project along with the appropriate association of custom fields to screens of new project.

It’s working fine.

We’re able to create a request in the new project. But not in the original project.

The error we got was “Status : 400, Bad Request”.

In case you faced a similar issue, please let me know how you’ve solved the problem.