Whenever I trade with a cartographer, I get an undiscovered map. I go out to discover the map. When I trade with the cartographer again, it gives me the same map even when the mansion/monument was discovered. If you already discovered an explorer map, The cartographer should give you a new undiscovered explorer map. Not only that, but sometimes the icon for the mansion or the monument wouldn't even appear on the explorer map.
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violine1101
migrated
whenever I trade with another cartographer, it usually gives me the same map to the same place.
Villagers always trade the same item with you. If you want to get a new explorer map, look for another cartographer. See MC-108082.