Possible bug in Ionic 4 in Angular Reactive Forms:

This is part of an evaluation of Ionic for me and to be honest it just feels a bit flaky. I have ‘fixed’ my issue, but don’t understand why what I did first time around doesn’t work… Maybe this is some form of noobie error but I don’t think so. I think the function names are pretty obvious but that isn’t the issue anyway.

I initialize a user details form like this:

 ngOnInit() {
        this.userDetailsForm = this.formBuilder.group({

         ... some stuff

          _Address: [],     // This is a holding string value for the pop over form.

          ... more stuff
        this.userService.getUserServer().subscribe (user => {
          this.userDetailsForm.patchValue(user);   // Note the _Address doesn't exist in the user obj.
          this.userdata = user;
          this.address = new Address(this.userdata.Address); // preserve original address data
          this.userDetailsForm.value._Address = this.address.fullAddressString();

          error => this.helper.showAlert('We cant connect to the server at the moment msg is:' + error)

The _Address value is to represent the address as a single string which is completed in a separate Ionic-popover (which all works just fine).
However in the form, with the Address string value like this:

      <ion-label position="fixed">Address:</ion-label>
      <ion-input type="text" (click)="getAddress($event)" formControlName="_Address">{{ userDetailsForm.value._Address }}</ion-input>      

It doesn’t work in the initialization part. It DOES work when I update it from the popover code.
If however, I change it to this:

      <ion-label position="fixed">Address:</ion-label>
      <ion-input type="text" (click)="getAddress($event)" formControlName="_Address">{{ addressString }}</ion-input>      

… and set the ‘addressString’ value in the ngOnInit function like this instead:

          // originally - this.userDetailsForm.value._Address = this.address.fullAddressString();
          this.addressString = this.address.fullAddressString();

It initializes and displays just fine.
If I log the value of the form _Address, it is also just fine. Just not displayed on initialization.
Many thanks.