Not sure if anyone has mentioned this further back, as I haven't read the read thoroughly, but.
Chain adjustment and condition is a big influence on gear selection smoothness.
Have a look at the sticker on the swinging arm and set the chain as close to 30mm freeplay as you can. revolve the wheel to find the tightest point in the chain and check the measurements there.
I use a steel tape from underneath and hook the tab on the top of the chain and then push it upwards with the chain. hold or lock the tape and let the chain go. The bottom of the chain should come down nicely to 30mm. I actually find it sweeter at 28mm at the tightest point, but go by the book to 30mm.
A worn or dry chain will effect the gears, as will hooked sprockets.
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