Yes, I saw the same on my 800, and no end of tweaking picture settings could clear it. I see it sometimes on black areas on Freeview too, and it's not a signal issue. Switching to the LG was a revelation. Nothing like that at all. Others here will almost certainly disagree, but I don't think that the picture on the Panasonic is that good. I've lost count of the amount of time that I've spend messing around with picture settings, trying to get things correct, to my eye. By comparison, five minutes of tweaking the LG picture and I'm done. I use LG's Cinema mode for all settings, and allow the TV to use its in-built DV/HDR settings. By comparison, the DV picture on the Panasonic was stupidly overbright and saturated, and although I managed to tame things to a degree, I just couldn't resolve the saturation. DV on the LG out of the box is fine by comparison, though maybe just a little too dark, but I can live with that.
Clem