LAWeekly has a profile of the Robotech franchise and here is an excerpt.
Robotech was a new idea for U.S. television as well as a work-in-progress. Because it was an amalgamation of three different series, each with a unique score, Robotech required all new music. That new score wasn't complete until 26 episodes into the series. The musical accompaniment for the first handful of episodes was essentially a rough draft. It wasn't until the series went into its third round of reruns that the music cues from that first handful of episodes were fixed. For a while, the sound of Robotech's original run had disappeared. "Nobody bothered to save the master tapes of the original mix because it was always perceived that this was an incomplete version of the show," says Yune. Years later, the Robotech team was able to retrieve those old cues thanks to a fan who had recorded the series onto VHS cassettes years earlier.