When Kenneth Drake is walking to the window to investigate the shrunken head hanging outside, there is a poorly placed splice (film "jumps") with the background (curtains suddenly appear) and lighting drastically changing.
When the family and the detective are gathered around the coffin, smoke is seen drifting into the shot behind the right shoulder of the family doctor. Nobody was smoking in the scene.
While examining Drake in his bed the close-ups show his eyes wide open, but when the camera pulls back his eyes are closed.
During the fight between Zutai and Jeff, the "blade" of Zutai's weapon is rubber, and keeps wobbling around, and bends when it brushes against anything. (Earlier they said the blade was bamboo, but even bamboo wouldn't wobble that much.)
After examining Drake lying motionless in his bed his doctor says there is no sign of a pulse, but in the closeup of him the pulse in his neck is clearly visible.
When Kenneth Drake's head is removed from the basket, the mouth is sewn shut. But when it is put into the kettle of boiling water, the mouth is not sewn.
During Rowan's climactic struggle with Zutai, the latter's obviously rubber knife noticeably wobbles.