The passenger side headrest on my 1987 560SEL has a minor promlem. When I engage the switch to raise it, it goes up just fine, however when I try to lower it, there is no movement. The motor lowers, but the headrest remains in the same position. If I rest my hand on the headrest (adding some weight) it will lower. Can I just lubricate the bars on the headrest, or do you think it is more involved than that. If lubrication would do the trick, what do you reccomend? Thanks in advance.