Firebase Firestore changing phone numbers

Question

I have been working with Firebase for over a year now. Today I did some testing and suddenly, Firebase changes phone numbers instantly to random numbers. I want to save the phone number as a string into Firestore, but everytime I update the Document of the Firestore, the phone number String is converted into a random number.

Can someone explain this to me? Is it becaue of the GDPR or privacy stuff?

Before updating the Doc:

After updating the Doc (input: 06601234567) , it becomes a random number (71032704):

I am working on a Nuxt Project.

Answer 1

Update: I implemented a wrong way of nullchecking in my updateDoc function. I wanted to set the telefonnummer field to null, if there was no input from the user. Apparently, it didn't work.

  await updateDoc(doc(db, 'test', userid), {

              //Input: 066012345678

              // Firestore --> -77123412
              telefonnummer: this.telefonnummer | null,

              // Firestore --> 066012345678 --> nice
              telefonnummer: this.telefonnummer,