Spring Boot Custom Exception showing most peculiar Behavior

Note - I have already set the flag server.error.include-message=always in application.properties

I have made a custom exception which should give a message to client when raised. However, that does not seem to be working whenever error code is 401/403. In that case I only receive a 401/403 status code with no response body at all, like below.

As soon as I change the status code to anything else, I start getting proper response body, like this.

    @ResponseStatus(value = HttpStatus.UNAUTHORIZED)
    public class BadCredentialsException extends RuntimeException{

    // Runtime exception just needs this, I guess :/
    private static final long serialVersionUID = 1;

    public BadCredentialsException(String message){
        super(message);
    }

}

See First antMatchers, that's where the concerned endpoint is.

SecurityConfiguration.java

@Override
protected void configure(HttpSecurity http) throws Exception {
    http.csrf().disable().
    authorizeRequests().        
    antMatchers(HttpMethod.POST, "/api/v2/user/login/**").permitAll().
    antMatchers(HttpMethod.POST, "/api/v2/user/", "/api/v2/user", "/api/v2/user/change-role/**").hasAuthority("ROOT").
    antMatchers(HttpMethod.GET, "/api/v2/user/", "/api/v2/user").hasAuthority("ROOT").
    antMatchers(HttpMethod.POST, "/api/v1/customers/", "/api/v1/customers").hasAnyAuthority("ADMIN", "ROOT").
    antMatchers(HttpMethod.GET, "/api/v1/customers/", "/api/v1/customers").hasAnyAuthority("EMPLOYEE", "ADMIN", "ROOT").
    anyRequest().
    authenticated().
    and().
    httpBasic();
}

My Thoughts and Observations

-> I can see my message in the terminal, that means the exception is definitely being raised. I have also tried logging something out in the BadCredentialsException file to see if its being raised or not, and yes it seems to be working.
-> There is a possibility that spring security might be deleting the response body on such status codes, although that's only a wild guess. I am going to try and disable spring security for a bit and see if I receive proper response body or not.

UPDATE - I have modified the post so that only currently relevant questions are being shown.