New Bike Sticky Shifter Issues

[GentlyBenevolent]

Had a bittersweet new-bike-day for the other half last week, due to some odd behaviour with the shifters. Long story short:
Bike: Dawes Giro 300
Shifters: Shimano 2300
Has had a new, shorter stem fitted, but with more rise. The original stem was much longer and in the "down" orientation.

When the RHS shifter is pressed in to move up the cassette it moves fine, clicks, but then doesn't always return. I tried various twiddling with the adjusters, but the cables just seemed too short.

Took the bike back to the shop today, and they've supposed to have fixed it. Tried it outside the shop and it was OK, but once we got it home it's sticking again.

The odd thing is that if I wiggle the cable while the shifter has stuck it'll release and return. The shifter also seems almost loose - like it's not hanging straight down, but to one side slightly. The bike is fine apart from this inconsistent behaviour. My questions boil down to:

Is this something I might be able to fix myself?
Is the shifter actually broken and needs replacing?

 

[SpokeyDokey]

It could be poor cable routing or too long a cable etc. The shorter stem will probably need the cables shortening.

Take it back to the shop and ask them to sort it properly.

 

[GentlyBenevolent]

If anything, because of the increased lift on the stem the cables might be too short. I had another look and everything worked fine, and the cables aren't as tight-looking after the shop visit.

We went out for a ride yesterday, and it stuck about 3 times in 12 miles, everything else was fine. I'm slightly loathe to take the bike back again as it's a 50 mile round trip. They've already had a chance to fix it, so next time it'll be a reject and refund. It's just so close to being spot on though.

 

[GentlyBenevolent]

Update: Took the bike back again and rejected it. After another little ride to check things it was clear there were a number of issues apart from the shifters - brakes were pretty dire, the gear change was quickly getting worse (more reluctant / shifting without operating the shifters), mounting lugs welded on skewed among other things.