Commented Unassigned: AsioOut dispose() - keep signal [16500]

Hello,
I'm reading some wave files using AsioOut and a WaveMixerStream32. Everything works great but I noticed that sometimes (1 time on 5) when I close and start again my program, I have a loud signal playing in the output of my audiocard and I have to restart the app to delete the signal and come back to normal.

I'm thinking it's the asioOut which stays open or something like that.
When i close the app, I'm doing the following :
1. I remove all the input stream in my audio mixer and I stop the asioOut
_asioOut.Stop();

2. After 0.5s, I dispose all the mixer, the channels and asioOut and set them to null.

Am I doing something wrong here?
How can I get rid of the loud signal ?

(My audio card is a Komplete Audio 6 and it's compatible asio driver)

Thanks for your help !
Comments: It happens at higher and lower latencies.