1/
Turning the volume knobs will not solve the issue, there is no audio on the output jacks whether the position of those knobs. After rebooting the audio is fine (without turning the volume knobs).
2/
By freezing I mean the audio stops working. The display and knobs are still OK and functional.
3/
I was using the Analog Factory midi keyboard, straight connected with a single and short midi cable, so there was no chance to create a loop.