I've put a new set in. Bike was running great last week but lumpy after a week of commuting. Do they stretch and if so, is it like a guitar in that it will take a while for them to achieve tension?
In my experience all cables will stretch a little after instalation, which may well account for what you are describing. It would seem normal to me to have to make some fine adjustments a week or so after fitting. But hopefully some of the more experienced with these bikes can elaborate.