Angular11 using promise throwing A client-side or network error occurred: Uncaught (in promise): [object Undefined] - es6-promise

Question

I have the following app initializer in my angular application. When deployed to test environment i am getting the following error
"A client-side or network error occurred: Uncaught (in promise): [object Undefined]"
app.module:
function initialiseApp(
appInitService: AppInitService
): () => Promise<SessionDetailsResponse> {
return async () => {
const sessionDetailsResponse: SessionDetailsResponse =
await appInitService.init();
return sessionDetailsResponse;
};
}
Here is my init service
#Injectable()
export class AppInitService {
private serviceUrl = '/v1/session';
private _http: HttpClient;
constructor(
#Inject(ENVIRONMENT) private _environment: Environment,
private sessionDetailsService: SessionDetailsService,
private httpBackend: HttpBackend
) {
this._http = new HttpClient(this.httpBackend);
}
init(): Promise<SessionDetailsResponse> {
return this._http
.get<SessionDetailsResponse>(
`${this._environment.apiBaseUrl}${this.serviceUrl}/details`
)
.toPromise()
.then((sessionDetails) => {
this.sessionDetailsService.update(sessionDetails);
return sessionDetails;
})
.catch((error) => {
handleUnauthorizedAccess(error, this._environment.baseUrl);
return Promise.reject();
});
}
}
export function handleUnauthorizedAccess(error: any, baseUrl: string) {
if (error.status === 401 && error.statusText === 'Unauthorized') {
const returnUrl = window.location.pathname;
const webUrl = `${baseUrl}/Account/Login?ReturnUrl=${encodeURIComponent(
returnUrl
)}`;
window.location.href = webUrl;
}
}