In the scene where George Fields and Michael Dorsey are arguing in George's office about Michael's being difficult to work with, the pen in George's hand and on his desk disappears between scene cuts consistently.
In the party scene, when Michael (out of drag) meets Julie and lays "the line" on her, she throws a drink in his face. The drink hits the back of the man behind them. The man jumps, but doesn't turn around. When Michael turns to dry his face on the man's coat, the coat is dry - and Julie's glass still has champagne in it.
When Sandy bangs on the door to Michael and Jeff's apartment, Michael removes his wig, tosses it on the dining table, and runs into the shower to remove his makeup. Jeff does not take the wig off the table, but when he let's Sandy in, the wig is no longer there.
The airborne panning view of midtown Manhattan (a transition shot after the montage of Dorothy's magazine photo-shoots, filmed above Union Square) is stock footage from the early 1970's or perhaps earlier; at least one skyscraper completed by 1975 is missing (the One UN Plaza towers).