Master deck switches randomly

 I kept the crossfader in the middle position during my last set and only used the upfaders and eq. During the set rekordbox started switching between the two decks randomly causing the pitch to go up and down on the playing track when I touched the vinyl of the track that was not playing at the moment.

I am using a DJM 250 mk2 with the rekordbox vinyls and a 2015 macbook pro running macOS 10.13.3.

Help would be much appreciated!