How can the "medicine man" have glasses at all, since the island is supposed to be hidden and relatively undiscovered from civilization? (Unless of course he took/found it from a dead soldier who was once stationed there - they say that the US and Japanese fought on the Island))
Many of the blows in the final fight scene obviously miss their targets and hit only air.
When the heroes return to the island and crash land the plane, you can see the steel wire pulling the wrack.
In the scene where the natives lead Bud and Terence to the jap tank, they both wear parts of US uniforms they took from the abandoned WWII US military depot.
Hill's shirt has US Air Force written on it, which is incorrect, as the USAF didn't exist before 1947, two years after the end of WWII.
Cameralights are reflected on the surface of the tank once it gets out of its hiding place. Also, you can see the lights reflected in the glasses of the "medicine man".
Under no circumstance would a Marine Major ever wear a New York Yankee Cap among his men and in front of civilians, and therefore, technically, be out of uniform.