Hi,

I'm running this tutorial and every time when I tried to close the gazebo simulation, although the GUI was closed, the terminal has no respond, and it seems still running in the background. So I have to use ^C to kill the programme. However it shows this everytime:

[gazebo_gui-3] killing on exit
[gazebo-2] killing on exit
[gazebo_gui-3] escalating to SIGTERM
[gazebo-2] escalating to SIGTERM
[rosout-1] killing on exit
[master] killing on exit
shutting down processing monitor...
... shutting down processing monitor complete
done

And then there will be no models in the world if I relaunch the gazebo. But it works fine if I restart the Ubuntu.

I'm using ROS melodic and gazebo 9.0 in Ubuntu 18.04 LTS. I solved this by upgrading my gazebo to 9.16, everything works fine even I relaunch the gazebo. However it still shows this error and the ubuntu will notice me that the gazebo has closed unexpectedly. I wonder why is that happenning, and is this going to influence any use of the gazebo?

Thanks.