Problem with grey(empty spots) on global_costmap inflater layer

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Hi, I am using my own diff-drive robot on ROS Melodic on Ubuntu 18.04.

When creating global plan, value of starting point on global costmap is erased. The problem is that global costmap is not refreshed and after multiple rides, I have many empty pixels. Thus next global paths are very curved. I will be really gratefull for some tip!

My costmap parameters:
    global_frame: map
    robot_base_frame: base_link
    rolling_window: false
    obstacle_layer:
       enabled: false
    update_frequency: 10
    publish_frequency: 1
    cost_scaling_factor: 6
    inflation_radius: 2 
    raytrace_range: 2

    resolution: 0.025
    robot_radius: 0.35
    footprint_padding: 0
    transform_tolerance: 0.5
    track_unknown_space: false

    plugins: 
        - {name: static_layer,            type: "costmap_2d::StaticLayer"}
        - {name: obstacle_layer,          type: "costmap_2d::ObstacleLayer"}
        - {name: inflater_layer,          type: "costmap_2d::InflationLayer"}

    obstacle_layer:
           footprint_clearing_enabled: false
           observation_sources: scan
           scan: 
             marking: true    
             clearing: true 
             data_type: LaserScan
             topic: sick_safetyscanners/scan
             sensor_frame: base_link
             inf_is_valid: false