Goofs

Gold bars that size would be a whole lot heavier. The guys should have handled them accordingly.

At the time of the mysterious disappearance the lighthouse was not equipped with radio, in fact radio-telephone technology was not available in 1900 at all.

Radio had been invented and demonstrated just a few years earlier, however, commercial radios were not available at this time.

At a couple of points in the movie references are made to "the radio" and in one scene radio audio can briefly be heard from the radio.

In 1900, the very first demonstration of a transatlantic radio transmission had only been demonstrated by Guglielmo Marconi a few years before, and by Morse code only, not voice. By 1900, commercially available radios had not yet been invented.

While commercial radio became standard in on ships not long after this event, it was not available in 1900.

The wind proof "zippo" type lighter wasn't invented until the 1935, several years after the era portrayed.

This movie is based on an actual event that occurred in 1900. However, in the opening scene as the keepers are approaching the dock and saying goodbye to loved ones, just after the camera shows Thomas approaching, it cuts to various people. In the background, a late 30s to late 40s stake-bed truck can be seen from the rear. While the exact vintage is impossible to discern from the camera angle it is at least 37 years too late of a model to be in this movie.

For that matter in 1900 to see any motorized vehicle of any kind would be considered an extreme rarity.

The film appears to be set sometime in the early decades of the 20th century, going by the way the characters dress, props etc. Yet the motor launch which takes the 3 men to the island appears to have modern looking antennae.

The dog on the island disappears during all fight scenes and also during any scene in which an additional surprise human being appears on the island.

Missing Dog? Previously mentioned dog disappeared? At times while James was beginning his alone time, struggling to maintain his sanity, he's seen hook in hand chasing the dog. At one time Thomas stops the boy (Donald) from running after James to stop him. (around the 1h10m mark and beyond).