I've been tasked with finding a bike for my daughter when she starts teacher training in September and have found a potential bike close to us. BUT the seller says that despite it only being used "a couple of times" the Sturmey Archer 5 speed hub doesn't shift between 3 and 5 very easily. A bit of a long shot I know, but is this a common problem, and if so is it likely to be easily fixed or the sort of thing to walk away from?