Under the "bulbed" rubber there are screws to remove the transition piece where the old caulk needs to be replaced. It takes time and patience to do it. Remove the rubber covering the screws. Remove the screws. Use a dull putty knife to pry the metal off. Use the putty knife to remove as much old caulk as possible. Apply new Dicor non-leveling caulk. Replace the metal piece/screws/ rubber "bulb. You may even want to order new rubber. It gets pretty stiff over the years. Hopefully you have minimal damage to the wood inside the walls.