Right before Kitai reaches the river, his father's cutlass is on his backpack. The cutlass disappears in the next shot, right before he starts building his raft, until Kitai picks up a new one at the crash site.
Before the crash, Cypher Raige straps himself into the chair with the X harness. In the next shot, he's in the background with no straps on. In the next shot after that, you can see he's strapped in again.
During the voice-over at the very beginning, Cypher Raige's ability to not be detected by the Ursa is described. It is stated that "This phenomena is known as ghosting". The correct singular form of the word is phenomenon.
When the asteroids get ejected from the wormhole along with the ship, they immediately begin to slow down. In space, however, they would continue in their speed until e.g. hitting an obstacle or entering the gravitational pull of a planet.