Continuity mistake: The conversation Tim and the others have at the hardware store becomes a lot different when Jill sees the (supposedly) same conversation on videotape. First of all, Tim's remark the "Jill's speech was so boring" has become "Jill's speech was so DULL". Secondly, Eddie's entire tale on how his wife wanted to change the fabric in the sun room is missing from the tape. And third, when Tim is talking about Jill's psychology studies, the expression "these terms" has become "these USELESS terms".
Continuity mistake: At the beginning of episode 4.10, "Ye Olde Shoppe Teacher", Tim's lopsided toolbox that he made turns 180 degrees as Jill pushes it away. As Jill and Tim are talking, it turns back. Then it turns 180 degrees again just before Tim briefly leaves the room.
Continuity mistake: In the opening segment, as Heidi hands Tim his hot-air gun, he takes it with both hands, then lets go with his left so he's only holding the gun in his right hand. The angle changes, and Tim is once again holding the gun with both hands, before he once again removes his left hand.