When Wade Anders goes into the office at the beginning of the movie to set up the crime, the clock on the wall indicates 7:25 p.m. After letting 4 cigarettes burn down (among a few other tasks), he leaves after about 10 minutes. However, the clock now shows 10:55 p.m. No way was he there for over 3 hours.
At the murder scene when Columbo notices the computer, the screen shows about one paragraph of writing on it, maybe 5-6 lines. The shot then switches to a close-up and the screen shows two paragraphs of writing. The shot changes back to a farther away view and only the one paragraph is there.
The camera in Wade's office is on a motion detector. In the beginning of the movie, the camera does not turn on until Wade enters the room. Later when he is editing the surveillance video, the camera records him walking up to the door and then opening it from the outside, even though the camera wouldn't have been recording at that time.
The floppy disc that Wade takes from his office is different than the one he uses to plant the story on Budd's computer. The disc, when he first takes it, has about 5 stories written on the label with a space between each title. When he takes it out of his pocket at Budd's house, there are more titles written on the label with no spaces between.