does not report parsing failure if a duplicate json key gets inserted when merging two translation json files

[folsze]

very easy to reproduce:
(german example)

de.json:
"World Countries": "Länder der Welt"

locations/de.json:
"World Countries": {
"Germany": "Deutschland"
}

Then when I merge with this, it will either take the first or second key, never both:

await this.appTranslate.loadAdditionalTranslations("de");

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { TranslateService } from '@ngx-translate/core';
import { firstValueFrom } from 'rxjs';

@Injectable({providedIn: 'root'})
export class AppTranslationService {
  constructor(
    private http: HttpClient,
    private translate: TranslateService,
  ) { }

  public loadAdditionalTranslations(lang: string) {
    const url = `assets/i18n/location-collections/${lang}.json`;
    return firstValueFrom(this.http.get(url)).then((data: any) => {
      this.translate.setTranslation(lang, data, true);
    });
  }
}

I don't know how such an important used library has such a bug of this not being reported as an error.