It almost sounds like the camera created frames at 29.97, but recorded at 59.94. That would be one way to get more light onto the imaging sensor. But I don't know enough about the way a GoPro shoots -- this is a guess.
If your GoPro set the shutter speed, which it does automatically, to anything less than 1/59th of a second you end up with duplicate frames. pairs of identical slices in tkme is the only option. It is also not uncommon.
To test the original footage create a new comp from selected footage then step through the timeline one frame at a time and look for duplicate frames. If you see them then the footage was shot with a slow shutter or the settings were wrong when the footage was imported through GoPro Studio.
Did you ever solve this issue? Did any of these responses assist you?