It would be nave to think that every bike is properly repaired or even properly serviced on the first go-round. I was a motorcycle dealer for many years and know that stuff happens. The screw-up may be due to carelessness, or it may due to a lack of communication between the shop and the customer. It's possible that the techs really can't find the problem or, in rare cases, the bike may well have some odd quirk that the owner will simply have to live with. In some extreme cases, and yes, it has happened to me, there may be bad chemistry between the two parties that causes one or the other, usually the mechanic working on the bike, to simply walk away mumbling to himself, fervently hoping that when he turns around the problem will have just disappeared. Trust me on the last one, it won't.