Yes, it can be a problem sometimes. Try to get the zero point as close to zero as possible, ideally under 30 millivolts. For reoccurring problems, it may be necessary to replace null sensor, PN #9865901. It is usually necessary to land the car on pipe stands and depressurize system, loosen vic, and shift muffler over to get clearance to be able to slide null sensor off of valve stem to swap part.
It is also worth noting that there is an up and down pilot filter screen in valve block, located under large hex head bolt heads. You can remove these to clean them when the system is depressurized. But do them , ONE AT A TIME as they are very easy to reinstall backwards because they look so similar, (example accidentally putting up screen in down side)
