simple keyboard delete button not working correctly -vuejs2

I am using a simplekeyboard for my project, I wrote the function of the delete button myself. I have an input and when I press the 1 key on the keyboard and then delete it and press the 2 key, it appears as 12 in the input. The old input value comes with it. How can I solve this?

My code is as follows;

SimpleKeyboard.vue

case "{delete}":
            this.screenStore.handleKeyboardChange(this.screenStore.inputs[this.screenStore.inputName].slice(0, -1));
            this.firstCharacter = true;
          break;

and screen.js;

handleKeyboardChange(value) {
      //console.info("handleKeyboardChange:", value, this.inputName, this.inputs);
      if (this.inputName) {
        //this.inputs[this.inputName] = value;
        Vue.set(this.inputs, this.inputName, value);

        eventBus.$emit('keyboard-event-triggered', this.inputName);

        var _this = this;
        this.checkinFields.forEach(function(field){
          console.info(field.id, _this.inputName);
          if(field.id == _this.inputName){
            var property = field.target;
            if(property === 'firstname'){
              property = 'firstName';
            }
            if(property === 'lastname'){
              property = 'lastName';
            }
            _this.appointment.visitor[property] = _this.inputs[_this.inputName];
            console.info(_this.appointment);
          }
        });
      }

    },

please can someone help me? I’ve been trying to solve this for days