Here is a pseudo function that is supposed to complete but it doesnt ObservableFunctionA iterates over an array of data, as it spits out the items ObservableFunctionB runs through each item

ObservableFunctionA(parameter1,parameter2)
            .pipe(
                mergeMap((res) => {
                //use res
                // -->parameter3,parameter4
                    return ObservableFunctionB(parameter3,parameter4)
                })
              )
              .subscribe({
                next(x) {},
                error(err) {
                  console.error("something wrong occurred: " + err);
                },
                complete() {
                  console.log("done");
                },
              });

This is ObservableFunctionB

const ObservableFunctionB = (p1,p2) => {
 
  return new Observable((observer) => {
    promiseA
      .then((res) => {

        //Do stuff

        observer.next(manipulatedRes);

        if (condition) {
          console.log("This is actually logged, the line below doesnt get executed!");
          observer.complete();
        }
      })
      .catch((err) => {
        observer.error(err);
      });
  });
};

The condition is reached, the line is logged yet the observer complete function is not called

Why?