Factual error: At the very start, the lead parachutist says they're jumping from 30,000 feet, the altimeter confirms it, everyone whoops and cheers, and he gets them to put their masks on just before jumping. Two problems - the plane they're in is a De Havilland DHC-6 Twin Otter with a maximum altitude of 25,000 feet. And at 30,000 feet in an unpressurised aircraft there'd be nowhere near enough oxygen for shouting and cheering - they all should have had their masks on already.
Plot hole: The poison is in the dog collar. Anson gets the poison from touching the collar. Why didn't the dog get any poison from the collar?
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Suggested correction: The poison cannot penetrate the skin as dogs don't have sweat glands on their bodies (except on the paws).