The Robinsons Were Here - S1-E4
Revealing mistake: After going beyond the perimeter fence for the first time, the children initially find the flowers that bloom when they each clap. When the robot motions to clap, you can see its left hand lost to the CGI flowers.
Shell Game - S2-E9
Revealing mistake: While Maureen and John are piloting their two maintenance pods, in the closeups which face each of them head-on, note the walls behind them have numerous identical smudges in their individual pods, which is especially noticeable in consecutive closeups.
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