Not working with more than 6 Crazyflies

Whenever I spawn more than 6 Crazyflies, I get this error:

[Err] [TransportIface.cc:395] Unable to connect to master.
[Err] [GLWidget.cc:856] Unable to connect to a running Gazebo master.
Segmentation fault (core dumped)
[gazebo-2] process has died [pid 12143, exit code 139, cmd /opt/ros/kinetic/lib/gazebo_ros/gzserver -u --verbose -e ode /home/esoria/catkin_ws/src/crazyflie_gazebo/worlds/basic.world __name:=gazebo __log:=/home/esoria/.ros/log/2f4ede52-11db-11ea-898d-d89ef326063d/gazebo-2.log].
log file: /home/esoria/.ros/log/2f4ede52-11db-11ea-898d-d89ef326063d/gazebo-2*.log

OR I don't receive the following

COMM: PARAM service init finished 
COMM: COMM init succeed 
SYS: Commander init finished 
SENSORS: Forcing sensors to SensorImplementation_sim
AK8963 I2C connection [OK].
LPS25H I2C connection [OK].
ESTIMATOR: Estimator type forced
ESTIMATOR: Using estimator 2
CONTROLLER: Using controller 1
SYS: stabilizer init finished 
SYS: Memory init finished 
SENSORS TEST PASSED [OK].
SYS: ALL TESTS PASSED ! System started... 
GYro Bias found 
GYro Bias found 
GYro Bias found 
GYro Bias found 
GYro Bias found 
GYro Bias found

In any case, I can't run more than 6. Is it a known issue?

Thank you for your work and help! Enrica

wuwushrek / sim_cf

Not working with more than 6 Crazyflies #15