Buttons not displayed in Rasa-X and Custom UI

I have provided four buttons in the response but bot showing only two. What could be the reason?

  - text: What do you want to know about {subject_cat}?
    - title: Entitlement
      payload: /FAQ_entitlements
    - title: Process
      payload: /FAQ_process
    - title: Duration
      payload: /FAQ_duration
    - title: Deduction
      payload: /FAQ_deduction


My one of friend have a same issue last time Still not got solution.