Is your 4DTV turned off by chance? IRDs like the 4DTV, if they have a VCII installed, will tend to cycle through channels looking for an active VCII channel, changing polarity, when you turn them off via the remote (they're still on relative to LNB power, etc, just the display goes off). Only other thing I can think of is that some IRDs have a setting which will turn off the polarotor control after a few seconds, as most polarotor motors will stay where they are set, however I think older polarotor motors needed constant control. With my old IRDs, I always set it to turn off the polarotor to save wear and tear on it. The IRD I have now doesn't seem to have that setting, or at least I haven't found it yet. Not sure if the 4DTV gives you that option or not. But if it is sending polarity control signals all the time, it might have a tendency to drift around. I know that with my current IRD, I was up on the ladder near the feedhorn once, and I could hear the polarotor moving around quite a bit, which I later found out was because I had some un-shielded wiring that was shorting out when it got windy. It wasn't unshielded originally, but the electical tape I had wrapped around it 14 years ago fell off.