Strange black ellipse computed by Global Costmap in Move Base

edit

When we ran our robot a couple of meters (approx. 100m), suddenly, several black ellipses and black dashed lines appeared on the map, and it turned out to be Global Costmap that generates these. The robot believes this is some object and tries to navigate around these black ellipses. But in fact, there are no objects near the robot and we're not using any lidar to navigate. Only GPS and odometry. So why are these be generated? Are we driving outside of the map?

![RVIZ] (https://imgur.com/a/YFpbBCV)

Anyone seen this before?

This is our costmap config for Global Map:

    global_costmap:
  global_frame: /map
  robot_base_frame: /base_footprint
  update_frequency: 1.0
  static_map: true
  rolling_window: true
  width: 20.0
  height: 20.0
  resolution: 0.010
  transform_tolerance: 10
  cost_scaling_factor: 0.0
  unknown_cost_value: 253
  inflation_radius: 0.0
  plugins:
    - {name: static_layer,            type: "costmap_2d::StaticLayer"}
    - {name: obstacle_layer,          type: "costmap_2d::VoxelLayer"}
    - {name: inflation_layer,         type: "costmap_2d::InflationLayer"}

Update, After I tried this config, the black ellipses changed to be just straight black lines instead:

global_costmap:
  global_frame: /map
  robot_base_frame: /base_footprint
  update_frequency: 1.0
  static_map: true
  rolling_window: true
  width: 20.0
  height: 20.0
  resolution: 0.1
  transform_tolerance: 10
  cost_scaling_factor: 0.0
  unknown_cost_value: 253
  inflation_radius: 0.0

Here is how it looks in RVIZ: https://imgur.com/a/ydkIur1