Time Machine 2.

Gumjad and his friends make another jungle trip with a local hunter as a guide. Along the way they run into the same old jungle bandits and try to get away by running into a cave. There is an earthquake; when they come out on the other side everything seems to be normal, but they’ve actually slipped into the past, in the middle of the war between two groups of ancient people. When one of these groups tries to steal their supplies, without any weapon, they have to use their portable radio to fool them. And during another earthquake they all go inside the same cave and finally come back to the present time.