Continuity mistake: When Andy Griffith and Dick Van Dyke shake hands at the club, The Judge is holding his pipe at a different height in the separate shots. (00:24:00)
Plot hole: The resolution of the case hinges on the fact that the culprit would be compelled by The Witness (whom they bribed, but who double-crossed them) to visit their stake-out apartment to try to dispose of their bloodied clothes. However, The Witness didn't and couldn't possibly know about that apartment. The murderer tried to prevent a non-existent threat that nobody made and did not worry at all about the other, very much more likely evidence and testimony The Witness provides - if The Witness was going to trick them to begin with, it makes no sense that they didn't just record the conversation, for once. The culprit does not even contemplate that possibility.
Continuity mistake: When The Judge is on the stand and Matlock approaches him to start his examination, Andy Griffith's right hand is on/off the railing, depending on the camera angle. (00:39:40)
Continuity mistake: Charlene comes back to the office after subpoenaing Piper Laurie. Ben is at his desk writing some notes. However, the pad turns 90° as the camera angles alternate. (00:19:50)
Answer: Leanne often went to the beach whenever she was upset about something. In this episode, Leanne realised that Kevin, the guy she had been seeing, had broken into her home and taken her diary in hopes of learning everything about her. This upset her because her privacy had been invaded and Kevin thought that the entries in her diary described the kind of man she was looking for. Ben drove down to the beach to comfort Leanne.
Only problem with that is that earlier in the episode LeeAnn went for a jog on the beach. She drives three hours to jog?
She didn't go for a jog. She went there because she was upset.