When Cordy starts swinging the floor lamp, the shade disappears/reappears several times.
(at around 33 mins) the ghost at Cordelias house is blowing cut strips of paper one of them gets caught on the back of Angels neck during two or three scene changes the paper disappears and reappears
Cordelia stays with Angel when her apartment is infested with cockroaches. After she showers, she is combing through her hair with her fingers looking in a coffee pot (because Angel doesn't have any mirrors). She sets the pot back down on the table and Angel walks past, you can see his reflection on the coffee pot.
(at around 50 mins) When Cordelia and Doyle are discussing Cordy's plans to take out a wall in her new apartment, there's a shot of the wall and a crew member's arm can be seen on the left of the shot.