Tactics Trainer odd choice of puzzles

There was a change in the tactic selection algorithm made at the end of April. It now gives a larger range of puzzles, centered around your current rating.
https://www.chess.com/blog/News/chess-com-dev-update-april-28-2017
and
https://www.chess.com/blog/News/chess-com-dev-update-may-26-2017