I did experience sound loss on the 4900 using wicked and I was watching a 24hr TV series channel.
What happened was I changed the channel and went back to the previous and there was no sound. I clicked left arrow button to bring up sidebar and audio option said disabled. I had to wait a few hours for it to come back. I never reported it to wicked because I hardly watch the channel and it was no biggie.
But I haven't experienced sound loss on regular channels on the 4900. Only the units using buzz tv4