Deliberate mistake: When Jen Moo and Ching fling back the fire bombs thrown by Leong Kit, they set the rear ends of his students on fire. But since they were all standing facing front and dispersed around the altar, they would be most unlikely to be hit that accurately in that particular place.
Deliberate mistake: When women are being shown naked by the x-ray machine, they look wrong. If the machine just sees through clothes, their breasts wouldn't look normal, but squashed together and supported by a bra.
Deliberate mistake: When the girls are done snorting the "coke" and Rick takes the tray away, none of the girls have snorted any of it because the same amount is still there except instead of lines it is now all muddled together. Also if you watch closely when they are snorting the coke, the rolled up bill only gets close to their nostril and not partially inside it. (00:09:45)