engine vs engine


currently watching the tcec engine tournament.. there is just a small but i think relatively big idea or worry.. stockfish is the strongest chess engine many would like to think though actually the current engine champion goes to Komodo who is currently behind Houdini (my favorite) . my question is how ist that in the same tournament Komodo beat stockfish and next game Komodo is beaten by fish..guys what's with the lack of consistency between engines.