startBackground function doesn't work all the time (for sound reproduction)

I'm trying to play a sound through an external audio card, by using the script below. I am having trouble because sometimes it works, but most of the times it doesn't work and there is no sound. I checked each step and everything seems fine. There isn't any error message.

Is there something wrong? Conversely, if I use startForeground, the sound is playing, but I can't use it because I need to work on the Command Window during sound reproduction.

d = daq.getDevices; %to know the ID of the sound card
s = daq.createSession('directSound');
ID =d(1,4).ID; %selection of sound card's ID
addAudioOutputChannel(s,ID,1:2); %the sound has 2 channels
sound = audioread('sound_2channels.wav'); %sound file
queueOutputData(s,sound);
s
startBackground(s)