Quick Shifter Woes.

After working fine for just over two years the quick shifter has stopped working on my wife's 2015 675 Street Triple. Took it to the dealer who fitted it, they said they adjusted it and it was working, picked it up and it was not working.
Did the trip again back to the dealer and they said there is no way to check out what is wrong, just need to fit a new one .......£400.00 please!

Would like to know if there is a way of checking out if it is say a broken repairable wire from the quickshifter, a software ECU issue or if as the dealer says I just need to bite the bullet and buy a new one.

BTW the dealer fitted the £200 option Q/S to the bike for free when new.

Cheers and hello again, it's been a while.