When Rance Burgess parks his hovercraft below the Heart of Gold, the mounted gun and brass shield are missing. The next time we see the hovercraft, they're back.
The first shot of Nandi waking up shows her hair loose on the pillow, and her hand curled up on the sheet beside her; in the next shot, a close-up, her hair is mostly tucked behind her ear and her hand is closer to her face than previously.
She turned her head slightly and moved her hand slightly, totally normal for someone waking. This isn't a Goof.
She turned her head slightly and moved her hand slightly, totally normal for someone waking. This isn't a Goof.
When Wash is shooting at Rance's men on board the Serenity, he is shown using a large caliber revolver. The chamber never revolves when he fires. And while he fires much faster than should be possible for a revolver of that caliber, they can be loaded with less powerful rounds, a .38 loaded in a .357 for example.
Near the end when Petaline shoots Rance, there's no gout of flame from the revolver, the hammer never goes back and the cylinder never turns.