When Steve is kissing Terry in the car in front of the Las Vegas hotel, the previous scene showed Malcolm closing the trunk, but through the rear window you can see the bright red trunk door is still up.
After their car goes off the road and down the hill in a grass field, a side view shows Malcolm driving on a road, then the front view has the car back on the grass field.
The last scene supposedly occurs during a premiere at Grauman's Chinese Theater but there are no hand or footprints in the forecourt as the stars walk red carpet.
After Malcolm fixes Terry's beater, he leaves a pile of spare parts directly in front of her vehicle, but she drives forward immediately afterward as if there were no obstructions in her path.
When the bull throws Malcolm after a short ride, you can briefly see a rope around its neck, presumably used by the stunt double. But the rest of the bull scenes show no rope.
Apparently, Tashlin was a little confused about Paramount's production schedule: Malcolm mentions having seen the Burt Lancaster adaptation of The Rainmaker (1956), which would not come out until after Hollywood or Bust was already released.
Entering Chicago, Malcolm drives down Lake Shore Drive north to south. As their journey is east to west going to California from the East Coast, they would have arrived at Chicago from Indiana, and not from Wisconsin.