Other mistake: Right at the start, as they're crashing, the computer narrates their rapidly-dropping altitude in feet. But the "altitude" dial we're shown is in metres. Most noticeable as they cross the 3,000 mark, when the computer voice and the height say/show the same number at the same time, despite the different units. 3,000m would be more like 9,000 feet, or 3,000 feet would be more like 1,000m. (00:03:20)
The Robinsons Were Here - S1-E4
Continuity mistake: Penny is holding an envelope in her hands, then turns around to follow the siblings and the envelope is gone. Just a cut later Penny has the envelope back. (00:32:30)
The New Guy - S3-E3
Visible crew/equipment: After Penny asks everyone on the ship to double-check that everything is tied down, when Will tells Robot that he thinks he found something to help them later, there's a yellow T-mark taped to the floor which is visible at the bottom of the screen. (00:31:20)
Answer: The Fortuna didn't have an Alien Engine. The cover story was the Fortuna was to explore Alpha Centauri but it was exploring the rift. The rift is what the Alien Engine creates and explains how the Fortuna was able to travel to a distant planet (what you call "galactic travel").
Bishop73