Non-blocking visualizer getting stuck when using multiprocessor/ multithreaded application

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### My Question

Hi everyone,
I am trying to display a constantly updating point cloud with the non-blocking open3d visualizer. For this I am using the following code, which I copied and modified from [Carla video tutorials-An in depth look at CARLA's sensors -CODE](https://carla.readthedocs.io/en/latest/tutorials/#video-tutorials) :

def add_open3d_axis(vis):
#Add a small 3D axis on Open3D Visualizer
axis = o3d.geometry.LineSet()
axis.points = o3d.utility.Vector3dVector(np.array([
[0.0, 0.0, 0.0],
[1.0, 0.0, 0.0],
[0.0, 1.0, 0.0],
[0.0, 0.0, 1.0]]))
axis.lines = o3d.utility.Vector2iVector(np.array([
[0, 1],
[0, 2],
[0, 3]]))
axis.colors = o3d.utility.Vector3dVector(np.array([
[1.0, 0.0, 0.0],
[0.0, 1.0, 0.0],
[0.0, 0.0, 1.0]]))
vis.add_geometry(axis)

vis = o3d.visualization.Visualizer()
vis.create_window(
window_name='Carla Lidar',
width=960,
height=540,
left=480,
top=270)
vis.get_render_option().background_color = [0.05, 0.05, 0.05]
vis.get_render_option().point_size = 1
vis.get_render_option().show_coordinate_frame = True
self.add_open3d_axis(vis)

start_time = time.time()
frame = 0
while time.time()-start_time