I've had my fretless Fender Jazz standard for a few years now, and recently the E string is radically detuned whenever (well, not always but quite often) I pick it up. I store it on a wall hanger, and carry it around in a gig bag. All the other strings are basically fine and the E string will be almost a D. The mechanism doesn't seem to be broken or loose or anything. Any ideas? Besides my roommate secretly joining a nu-metal band?