my two cents
Make sure you are shimming using the gearbox shell, gears and bushings only for initial test fitting.
test fit the shell halves by holding them together in your hand and use a small push device to test for side to side lateral slop in the gears by pushing back and forth on the gear shafts individually.
add or remove shims as needed, keeping the spacing of the gears from each other, also a priority. You don't want a gear pushed up on another gear. gears work with gears, not gear bodies trying to turn against one another.
You also want to make sure the tappet plate can move freely once the two shell halves are together. or the sector gear isn't shimmed too high and its pushing on the tappet plate. This will torque the tappet away from the delayer and can lead to tappet failure. Everything is happier when it moves in a straight plane of motion for optimum engagement.
for the final test screw it together and check for spin and any lateral movement including free tappet movement.
next, check the sector gear engagement point on the piston, does it need it's aoe corrected? is the piston seated properly in the guides during reassembly or is the piston jumping out of the guides during operation? It might need a new piston.
Does this aeg use a ball bearing spring guide or piston head, this will also smooth things out.
if free movement of the gears, sector engagement is good then reassemble, check the tappet plate is moving freely, plug in the battery, test once, adjust motor height if needed, carefully, see if it smooths things out and cycles better.
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