Gaffes

The blue cloth belt Cassidy Gifford wears on her jeans shorts is missing when she is outside the cave, 42 minutes into the movie.

While one girl is climbing up, the rope begins to swing. With the girl hanging in there with full weight, it is not possible for the rope to swing without the girl losing height, which only happens significantly later.

The natural light entering the cave where Cara, Jackie, Taylor and Veeves rappelled down should have rapidly alternated with the changing of day and night after they crossed the time warp threshold, just like it did for Dr. Hopper.

Unlike the cave that Prof. Hopper and Furby enter, the cave that the others enter isn't in direct sunlight. It has a small entrance under trees, that opens into a rather large cavern, the cave they descend down is at the opposite end of the cavern from the entrance. It would be nearly impossible for them to see the flickering of the seasons at the speed the days were passing.

In the 29th minute they first see the advent of time passing quickly through an opening in the cave, allowing them to see the sky. But it is always light outside. Even if night represented only eight hours of each day, then one would see the skies passing in darkness one third of the time, hence there would not be constant daylight visible to the eye or entering the cave.

One minute equals 15 years, with one-third of that being night. That's 3,652.5 minutes of daylight and only 1826.25 minutes of darkness passing by each minute in the cave. You wouldn't notice the darkness passing at that speed. However, it is represented by what looks like the shadow of a spinning blade on the walls of the cave when not looking directly at the sky.

When the main characters use the 'magic' ladder there are visible welds in the metal, which going by the insinuated technology shouldn't be there.