Hi! I just discovered that one of the four screws holding my A string tuning machine against the scroll can't be tightened or loosened. It just somewhat spins easily in the hole, but is still holding fast (doesn't drop out by itself). So far, it doesn't seem to be a problem as the tuning machine is still secured against the scroll and the bass still tunes smoothly. Any idea what's going on? Are the screw threads or maybe the screw hole stripped perhaps? Is this something I should be worried about? Any potential remedies would be appreciated as well. If it's any help, these are indeed some pretty well aged tuners on a rather old bass. Thank you so much for any help!