I've seen this pretty much on most of the channels at one time or another. Sometimes I can simply change channels up or down and that corrects it. Sometimes I've had to do a soft re-boot. There has never seemed to be a pattern to it.
I'm not sure about the 942, however on the 811, I just hold in on the power button for about 10 seconds, let go and it automatically starts re-booting.
What gets bad is when you have 2 or 3 tuners around the house on the same channel and they all buffer the content just a little bit differently. You can really get some weird reverb effects going until you change channels and put them back.