When the prisoners escape from the ship, Governor Koong is dressed in a nightshirt. But during the close-up when he says "I want those Roonstones" he is suddenly wearing his uniform.
When Nilz Yomm applies a medicinal spray to his wife, his arm completely disappears for a couple of frames.
R2-D2 has been hit by a molecular disruptor and has shrunk to the size of an action figure. When the effects begin to wear off, he begins to grow back to his original size while standing on a table. But in the next shot he appears to have grown smaller again.
When Gaff stabs himself in the leg by accident, the section of his cape that is visible between his arm and his body disappears for a couple of frames.
Near the end, when Admiral Screed leaves the volcano in his Imperial shuttle, an outer space background is visible instead of the blue sky around the volcano. This is because the footage of the vehicle lifting off is actually taken from the scene where it first landed in Tail of the Roon Comets (1985) played backwards.
Governor Koong normally has four fingers on each hand. But in several scenes, he suddenly has five fingers on each hand.
When Auren explains how the funnel works during the Drainsweeper race, the bare skin on her right arm is the same color white as her outfit during her close-up.
After Bun-Dingo is eliminated from the race, Gaff is seen standing behind a railing, but his left leg is positioned in front of it by mistake (the animation cels were layering incorrectly).
Mungo embraces Auren in the final scene. When it cuts to a close up of C-3PO, the background plate remains the same.