charge strip is on the side of the rail, normal issues are charge pin wear causing shortening of the pin and reducing contact to the charge strip or dirt between it and the copper strip, or wear in the rollers allowing the carriage to lean, pulling either the charge pin away from the strip or the pinion away from the rack, or the pinion gear if dirty again reducing its contact points with the rack
so check the rollers for wear
the charge strip is clean
the charge pin is clean
the condition of the charge pin
the condition of the pinion gear
