The masthead unit of the wind indicator jams at random and needs to be serviced. Silva has no spares and suggest: It is not possible to grease the bearings in the mast top unit. And unfortunetly we do not have any spare parts left for the 4000 instrument and transducer. You will have to buy a new set. Please contact your local dealer who can help you with this. Does anybody have a spare bearing for sale? Which brand is HR using today, or recommended? Many thanks and best regards Kurt Maring