I've had this piece of equipment for some seven years now.
A few months ago, I switched from using the YPbPr outputs on the PVR to composite video, due to my TV being older and not having very many inputs. I needed the TV's YPbPr for another piece of equipment, and so I switched the PVR to the remaining composite video input.
I noticed that there was a small bit of jitteriness in the video, but it was watchable. A few weeks ago, though, a more serious problem developed: that of a "blinking" flicker: brief periods of the video momentarily going black, like the blink of an eye. Particularly occurring on recorded program playback, but live also. These blinks might be isolated, or come in small clusters.
Yesterday, without powering it down, I blew dust out of the unit with compressed air (by blowing through the slits in its case, without opening it): the first cleaning it has received.
All the problems seem to have gone away; the composite video image quality is better without the jitter, and I haven't seen so much as one instance of the the black flicker.
I checked the temperature of the CPU heatsink and other places on the board with an IR thermometer gun. It seems to be running a few degrees cooler than before.
The problem might not have been thermal; perhaps some circuit in the composite video area (e.g. oscillator) is sensitive to the presence of dust (due to parasitic capacitance or whatever).
Prior to switching to composite video, I don't remember these problems. When the black flicker came on, I didn't bother trying to see whether it was also seen on component video.