The character played by Frances Bay is in two different spots of the sex clinic at the same time - the lecture hall and the library.
Trabucco does not use the same code to open his suitcase throughout the movie (sometimes the code has more numbers than others)
When Victor Clooney confronts Dr. Zuckerbrot at the hotel he rips the doctor's shirt open, but when Zuckerbrot leaves the room a few seconds later his shirt is buttoned and his tie is in place.
When Clooney is looking into the auditorium at the clinic, the door opens outward as seen from the outside. When the shot switches to the inside, the door opens inward.
When Victor describes everything he left behind when he abandoned his wife for Celia, among the things he lists is "the Betamax." However, Betamax was not introduced until 1975, and he says he has been married to Celia for twelve years, meaning they would have been married in 1969, so his first wife could not possibly have had a Betamax for him to leave behind.
When they arrive with the pregnant woman at the Zuckerbrot clinic the crew and equipment are more than once reflected on Trabucco's car.