REST API service returns 500 error which is actually 404. Same working expected by calling IP address of the service

We are facing a server related issue in one of our API Service application (ASP.NET WEB API 2). When we access the service by site domain name (api.xxx.com), the service returns an Internal server error (500). But If we accessing the same service by site IP address (11.111.11.111), Its returning proper result (404). This issue occurred only if the server trying to return 404.

What I have tried:

<pre>
https://api.xxx.com/api/Test/getEmployee/1 [Returns 500 Error]
https://111.11.111.11/api/Test/getEmployee/1 [Got Expected Result(404)]

Its working fine for the same API service and different params which is having data.

We have checked in code side, no error logged.

We hosted the site in Azure server.

Is there any problem with the domain name hosting/ load balancer/ ARR server.

Please help us to solve this issue.

Thanks in advance.