How come the Elections Department keeps redrawing the constituency lines?

Answer 1

To keep who ever appointed them's party in power. Just another way corruption is built in to the system.

There are also legit reasons to move lines, like shifts in the population, if there are more people in one part of the state they need smaller districts (geographically smaller) or if the state gets more Representatives, or less Representatives biased on population the lines need to be moved.