Check out example codes for "More than one custom value accessor matches form control with unspecified name attribute". It will help you in understanding the concepts better.
Code Example 1
The problem here is: the ngx mask and angular material datepicker combined, they cannot be combined!
It is a limitation of Angular
<div class="form-group">
<label class="control-label col-lg-2 text-right">Birthday</label>
<div class="col-lg-4">
<input type="text" class="form-control" formControlName="birthday" placeholder="MM/DD/YYYY" mask="00/00/0000" autocomplete="off" bsDatepicker>
</div>
</div>
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