Continuity mistake: In the scene with David and Gareth in David's office, David gives a hole-punch to Gareth as a souvenir. The hole-punch has a guide accessory sticking out of it (to punch holes in the middle of different sizes of paper), which is adjustable. At the beginning of the scene it only sticks out by about 2 cm, but by the time David hands it to Gareth it is about 5 cm - even though no-one has touched it.
Continuity mistake: When Donna comes in late and David is asking her where she has been, as it changes shots between Donna and David, in the background Dawn's right sleeve changes from being down to up at wrist height several times but she is in the same posture all the time.
Continuity mistake: Often during the show, the viewpoint will switch between cameras to show people from different angles. The problem is, the show is meant to be seen as a documentary, and filmed "for real", meaning these camera switches would reveal the camera that must have been taking the previous shot. No cameras are ever seen, and as a "documentary" it can't be said that the filmmakers could ask the characters to stop in mid-conversation while they moved the previous camera out of the way.