Likert questions defaults to answers with value "0"

Likert elements pre-selects default values even if not asked for this.
I was struggling to find particular case, but finally nailed it down to example bellow.

epic_question:
  '#type': likert
  '#title': 'Your state recently?'
  '#questions':
    EPIC1: 'How was your mood last week ?'
    EPIC2: 'How are you feeling today ?'
  '#answers':
    100: 'No problem'
    50: 'Lite problem'
    0: 'Big problem'

With this yaml, form opens with last answer selected by default
NOW.. if you change value from 0 to 1, it works as expected. No default selection in form.