I had my machine for a few years before needing to take it in for a standard service call. When I got it back it was dripping oil from underneath and the tension was all wonky. I brought it back and was asked how often did I clean out the bobbin area. It was implied that I wasn't doing it often enough or maybe not assembling the hook area correctly. I clean the bobbin area after every bobbin change and under the needle plate area quite often. Friends say I may be a little obsessive. I think the shop just didn't want to admit to doing a poor cleaning job. I may look for another shop next time.