Hi. I've been having an issue with the tail lights in my car, that occurs sporadically. There is a warning on the dash that tail light is off when I turn these lights on. It actually is off. However, the light reacts if I tap the lens cover. It then turns on and stays that way until I turn them off and back on the following time. This is not such a serious issue, I believe, but I would like to get it fixed. What do you suggest I should check? Thanks.