The value of textarea will be readonly after patching its value in the Angular 6 Formbuilder

I’m using the Angular6 formBuilder, in my form I used a Textarea element that its value will be generated by selecting an option of a radio button, the value of textarea will be readonly after patching its value with javascript.

HTML:

<textarea class="form-control"
 id="emailText" formControlName="emailText"></textarea>

Script:

bonusForm: FormGroup = this.fb.group({
    businessId: ['', Validators.required],
    TPC: [10000, Validators.required],
    emailIsSent: true,
    emailText: ''
  });

.
.
.

this.bonusForm.patchValue({
        emailText: `Dear ${this.data.ownerName},nwe just assigned
        bonus ${this.bonusForm.value.TPC} TPC for your great business
        ${selectedBusiness.name}`,
        businessId: this.businessId
      });

Screen shot:

enter image description here

What is the problem?

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Source Url The value of textarea will be readonly after patching its value in the Angular 6 Formbuilder