In the second video, why does the map go blank (other than the path traveled) at about 0:43, and then it seems to start from scratch again? I'm also not famili

In the second video, why does the map go blank (other than the path traveled) at about 0:43, and then it seems to start from scratch again? I'm also not familiar with the "cloudiness" of poorly mapped areas. I'm familiar with what the ROS Navigation stack/rviz looks like when it does mapping, though as a user rather than an implementer. Maybe I'll find the cycles to actually play with implementing this library someday soon.