When Longolius (David Sheiner) confronts Mara (Diana Hyland) for her failure, his gun alternates from left hand in long shots to right hand in close-ups.
Solo kneels down in the dusty saloon and when he stands up, his trousers have a lot of dust at the kneecaps. The next shot the dust has completely gone.
The Prospector (J. Pat O'Malley) uses an old fashioned plunger-style generator to detonate the dynamite. But it's never wired to anything.
Before Longolius slaps Mara, there are shadows of moving cowboys against the back wall even though they are supposed to be standing still while holding Mara.
Over the course of the climatic gun fight, Solo fires at least 10 shots out of his 6 shot revolver.
At one point Solo asks for as martini with two onions. Martinis are made with olives; a Gibson is made with pearl onions.
At the pool, Mara asks Napoleon if he wants a martini. "Yes", he says. "Very cold, on the rocks, easy on the vermouth". The martini she serves him has no ice.