If the closing wheel is off center, Sauder says, you may be running the wheel right over the seed trench instead of along the sides. One way to check is to put the planter on a piece of concrete. Lower the opener lightly onto the concrete, and pull the planter ahead a couple of feet. The closing wheels should be centered on either side of that scratch. A rusty chain can destroy a tuned meter.
Chains running over worn idlers make the chain jump.
They wear out surprisingly fast. On vacuum planters, use of talcum is critical. Static buildup causes the seed to spray down the seed tube. Talcum takes care of the problem. Graphite helps the fingers hang onto the seed.