Hi everyone I am having a small tuning issue with my bass. What happens is that one string (the D) doesn't change its pitch very well when I I try to tune it up or down, it tends to stick and then it goes about a 1/4 tone in one go. It makes it difficult to get the string perfectly in tune. I am suspecting that it is not a problem with the machine head but just that the string is not moving over the bridge properly. Someone was telling me that a good way of dealing with this is to get some pencil graphite on the bridge to act as a lubricant for the string and I wanted to check out if that was a sensible idea or not before I try it. I don't want to risk messing up my new expensive strings and the problem is not really bad enough to merit a special trip to my repair guy. Many thanks for any advice offered.