"Heart of Glory," Star Trek: The Next Generation Season One
Rewatching the series from the beginning, it quite jarring how different some of the sets were. The detention cell in this episode is way less elaborate than the set used later in the series. There also various neat little computer station and nooks and crannies seen throughout season one that never seem to reappear.
Just guessing, but anything that looked like a computer, would have been slightly altered, and used on a different set, and then slightly altered again and used on a different set and so on and so on.