Hi Igor,
I couldn't at first understand why you didn't hear any problems as hissing around every s & c in words. I had already updated to the latest version and the problem still existed. I came to the conclusion that problem must be with my equipment. I then played the show through a different monitor and speaker, and it sounded fine. This is the first time I've had problem with this speaker which is of a reasonable quality. A recent musical harmony sounds perfect but having gone back to a previous show with voiceover that too is now distorted. So, it's a new speaker on my Christmas list.
Thanks for taking the time and trouble on my behalf it is very much appreciated.
Regards
Steve