Again, thank you guys for your input. I have done various test (also tried to fade out volume with xvol option in AMP section), still this weird noise is noticeable. I’ve done these tests in completely new project, I’ve reset device to factory settings, and also uploaded again latest firmware. I’ve also put various signals sources to OT, and final result is still same.
From what I managed to specify, it’s probably not necessarily a crossfader-related problem, because FUNC + Level changes the value for MAIN and then I also hear these additional noises.
But ultimately, I will probably send this unit back to the store tomorrow and ask for a refund. I don’t think I want to test the second unit - I’m afraid that this issue is a ‘feature’ that from ever be in OT, just not everyone pays attention to such ‘small’ details. For me it’s just unacceptable, not for this money. Certainly in a normal situation I would not pay attention to it, I was just testing a crossfader with the simplest possible (as I thought) function. And because of that, I’ll probably always hear it.