SQL Tracker_store affecting conversation flow by giving "action_default_fallback"

Rasa Open Source
1 
tracker_store:
    type: SQL
    dialect: "mysql+pymysql"  # the dialect used to interact with the db
    url: "localhost"
    port: "3306"
    db: "rasa"  # path to your db
    username: "root" # username used for authentication
    password: "Password" # password used for authentication

these are my endpoints for storing the conversation. Also, these endpoints works properly and store the conversation successfully in event table. however, i am facing issue in my conversation cause of giving “action_default_fallback” after some conversation.