Audio problem: In the Russian bar scene the female bartender cycles a pump action shotgun at Dutch when she is holding a double barrel shotgun. Dutch then disarms her, when he turns the shotgun back on her you can hear a pump action shotgun being functioned and an empty shell hitting the floor. Dutch is holding a double barrel shotgun in the scene.
Audio problem: In the scene where Dylan is explaining the Decepticon's plan to Carly, there is a shot of Sentinel Prime moving the control pillar into the tower. During this shot, if you look to the left, you can see that Dylan's mouth is not moving when he is supposed to be talking.
Answer: Mudflap and Skids (the two idiot robots I believe you are talking about) were removed from the film due to negative fan reaction. While we don't hear what happened to them in the context of the plot, no reason not to assume they were killed in fighting between the movies. Arcee and Chromia (2 of the motocycles) were killed in the last film.