I bought a (new) Trek Crossrip recently, which has a Shimano Sora groupset, but with a SRAM 11-32 cassette.

I noticed that some of the gears (somewhere between 5th-7th gear) would sometimes be a bit "indecisive" when changing, and shift down, then up again, making me nudge the lever again to shift up.

I thought this was just cable stretch on a new bike and after a few weeks took the bike into the LBS for its post-sales service, mentioning the issue. They supposedly adjusted the gears, but it seems simply to have move the same behaviour to slightly higher gears (around 7th-8th). They may have just tweaked the limits, but not actually addressed the indexing. I'm not actually sure how how a continuous system operated with a cable can be set to jump precise amounts. Is it all just a question of cable tension?

Is this kind of thing normal? I know I have an entry-level groupset and not a Di-2 Dura Ace, but it's a bit disconcerting to have gears change by themselves.

As a comparison, I tried someone else's bike using an fairly old MTB groupset (XTR?). The gear changes felt smoother on this bike, but I sometimes found I had to click the lever twice to actually shift gear for some changes.

I know most gears are fundamentally mechanical and analog, so there is probably an element of "feel" to changing them. Is this something I just need to learn?

Thanks!

John