The amount of gold in their backpacks is much too heavy to be carried and tossed around as shown in the movie.
A gold brick weighs about 27 pounds (400 troy ounces). They dug up close to 60 of them, which would weigh about 1600 pounds. 5 guys would have to carry 320 pounds each. The Bloods would not have been able to lift that much, let alone carry it on their backs for miles.
When Seppo steps on an unexploded landmine, it's maybe 2ft onto the shoulder of a maintained, well-used road, which is basically-impossible (unless the mine is freshly buried, recently); Either the mine would have already been triggered years ago, by normal use of the road. Or if no-one had passed by to trigger the mine in the 50-odd years since the Vietnam War, then the road would be overgrown, unusable, and barely even recognizable as "a road".
M16's did not have a burst setting in Viet Nam. It was full auto or semi auto so they could unleash a full 30 round burst if need be.
M-16s firing at full auto for 20 or 30 rounds is silly. Most guys had them set for short burst or they would be out of ammo all the time...
At about 1 hour 8 minutes into the movie when David is walking down the hill to "make a deposit at the bank", he walks past a pink pin flag. This is most likely something the filming crew put down as a "mark" for the actor. At the very least, it shows that someone had been there rather recently.
Movie shows the returned soldiers boarding a small boat on the Saigon River of Ho Chi Minh City and departing upstream... Next shot shows them traversing in the same boat, the narrow jungle canals of the Mekong Delta, but they are located downstream.