I tried the following code
#!/usr/bin/python
import ibmiotf.device
from time import sleep
options = {
  "org": "uguhsp",
  "type": "iotsample-raspberry",
  "id": "00aabbccde03",
  "auth-method": "token",
  "auth-token": "MASKED"
}
def myCommandCallback(cmd):
  print('inside command callback')
  print cmd
def main():
  client = ibmiotf.device.Client(options)
  client.connect()
  client.commandCallback = myCommandCallback
  while True:
    sleep(1)
if __name__ == "__main__":
  main()
which is essentially similar code as yours.
And I am able to publish the commands to reach the device.
Can you please confirm if only 1 device (or simulated device) is using the device credentials and that the credentials are not being shared by multiple devices (either physical device or simulated device)?