The adventure they're currently doing (not U1) is an
exact replica of an adventure done shortly after the campaign started, on the same site, with the same opponents, and so forth. The current PCs won't really become aware of this (right now they just assume the place has naturally restocked itself ovr the years) until they take a few specific "unique" things back to town to sell off and run across some exact duplicates...and some very curious shopkeepers!
I'm hoping that in the long run one of the higher-level groups takes on the challenge of finding out how this dungeon managed to exactly replicate itself over about a 4-and-a-half year timeframe, because there is an explanation; and if something isn't done it'll keep replicating itself every now and then once a certain individual realizes it has once again been cleared out.
The adventure that didn't get finished has a group of PCs sent into the town - which is the capital city of a faded empire - on a mission to either find out what's gone wrong with the Emperor (over the last few years he's kinda gone balls-nuts crazy) or, if they can't or if he really is irredeemable, kill him off. Completed play got those PCs into town and starting to dig for info, that's it.
This adventure would in theory have happened not long before the current low-level group got going, meaning the city might still be a hornet's nest. Oh, well...