I was experiencing the same issue and googled for answers, after which I tried many of the suggested solutions and what seems to have worked is the following:
Pull L1 up as far out as socket permits and blow (or vacuum) all dust and debris at all angles (360°) and then add just a dab of petroleum jelly, making sure it covers all the visible surface of the rotating ball of L1. It seems to have worked. Just a dab.