Looks like you use fact, that in map all pairs are sorted. It's true for normal map(because it's based on BST), but wrong for unordered_map(because it's based on hash table and keys are sorted not by value, but by hashs)

std::map and std::unordered_map have different iterator invalidation rules. Basically, any std::unordered_map iterator can be invalidated after any insertion or deletion because of rehashing, and you can't control it. On other hand, std::map iterator is guaranteed to be valid until you erase it explicitly. That's why you got 2 different results.