In the scene where the weather is storming, the wind is blowing sheets of rain one way, yet the waves on the lake in the background are blowing in the opposite direction.
Clear use of wires when Hawk is thrown by bear.
Obvious dummy dog falling over cliff in opening sequence.
Obvious dummy for M'Rai when he is killed and thrown by the bear.
Obviously stuffed bear to represent dead monster-bear floating in the lake.
When Maggie Verne is seen leaving the helicopter during the rain storm there is a wire visible holding her handkerchief in place so it doesn't get lost in in the winds when she purposely lets it fall out of her pocket
Despite the movie supposedly taking place in the Maine woods, foliage and landmarks clearly show the area of the forests of British Columbia, where the movie was actually filmed.
Dr. Verne and his wife fly from Washington D.C. to Maine, but when they pass over a lighthouse on the coast the plane is clearly traveling south.
In the opening sequence, the dog can be seen to be hanging over 40 feet above the ground. Yet the bear (unseen) manages to pluck it down, despite clearly being too short in later scenes.