Angular recursive observable array fired complete before real end

I have an object that can has children. I have a function to insert or update instance (and children). But I have a problem with observables.

When I use forkJoin, the HTTP request (createSite or updateSite) is never execute and the complete is fired instantly. Now I use combineLatest, calls are executed. But the complete event is fired before all observable are ended.

I have also tried expand for children, butit loop and create a lot of time the same instance.

function save(): void {
  combineLatest(this.updatedSites.map(s => this.upsertSites(s)))
    .subscribe({
       complete: () => // somme actions,
    });
}

upsertSites(site: Site, parentId?: number): Observable<any> {
  const sourceSite: Site | undefined = this.sourceSites.map(s => s.findSite(site.id).at(-1)).filter(s => !!s).at(-1);
  if (sourceSite && !this.isSiteDeepEqualWithoutChildren(sourceSite ?? { label: '' }, site)) {
    return this.siteService.updateSite(site.id, site.label, parentId)
      .pipe(
        catchError(error => {
          console.log(error);
          return combineLatest(site.children.map((s: Site) => this.upsertSites(s, site.id)));
        }),
        mergeMap(() => combineLatest(site.children.map((s: Site) => this.upsertSites(s, site.id)))),
      );
  } else if (!sourceSite) {
    return this.siteService.createSite(site.label, parentId)
      .pipe(
        mergeMap(data => {
          site.id = data.id;
          return combineLatest(site.children.map((s: Entities.Site) => this.upsertSites(s, site.id)));
        }),
      );
  } else {
    return combineLatest(site.children.map((s: Entities.Site) => this.upsertSites(s, site.id)));
  }
}

What did I do wrong ? What did I misunderstand ?

So after some thinking, I have found a solution. Here it is if someone needs it :

function save(): void {
  forkJoin(this.updatedSites.map(s => this.upsertSites(s)))
    .subscribe({
       complete: () => // somme actions,
    });
}

upsertSites(site: Site, parentId?: number): Observable<any> {
  return new Observable((subscriber) => {
    subscriber.next(site);

    const upsertChildren = (site: Site) => forkJoin(site.children.map((s: Site) => this.upsertSites(s, site.id)))
      .subscribe({
        complete: () => subscriber.complete(),
      })

    const sourceSite: Site | undefined = this.sourceSites.map(s => s.findSite(site.id).at(-1)).filter(s => !!s).at(-1);
    if (sourceSite && !this.isSiteDeepEqualWithoutChildren(sourceSite ?? { label: '' }, site)) {
      this.siteService.updateSite(site.id, site.label, parentId)
        .subscribe({
          next: () => upsertChildren(site),
          error: error => {
            console.log(error)
            upsertChildren(site);
          },
        });
    } else if (!sourceSite) {
      this.siteService.createSite(site.label, parentId)
        .subscribe({
          next: data => {
            site.id = data.id;
            upsertChildren(site);
          },
          error: error => {
            console.log(error)
            subscriber.complete();
          },
        });
    } else {
      upsertChildren(site);
    }
  });
}

I use forkJoin and it works now. In fact, I have miss some information in the documentation :

[...] complete immediately if an empty array is passed

RXJS - forkJoin

So I give a value to the next and then complete my custom observable. So thing I found dirty is that I give a unused value to the next but it works !